# SLICC SLE classification criteria

SLICC SLE

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/slicc_sle`
HTML: https://magentlab.com/docs/slicc-sle
Markdown: https://magentlab.com/docs/slicc-sle.md

Not a medical device. Not a diagnosis, dose, or listing recommendation.

## What it computes

Apply the 2012 SLICC classification criteria for systemic lupus erythematosus (Petri Table 3): return clinical_count, immunologic_count, the biopsy-nephritis shortcut, and whether the published rule classifies SLE. Not a diagnosis.

## When to use

When an agent already has caller-assigned Petri 2012 clinical, immunologic, and biopsy flags and needs the published SLE classification result for research, not a diagnosis, not 1997 ACR, and not 2019 EULAR/ACR.

## When not to use

- Not a medical device and not a diagnosis of systemic lupus erythematosus. Classification criteria for research (Petri 2012).
- Not the 1997 ACR SLE criteria and not the 2019 EULAR/ACR SLE classification criteria.
- magent does not examine skin, assay serologies, or read a biopsy. Caller assigns each flag. Criteria need not be concurrent.
- Direct Coombs’ test counts toward immunologic_count only in the absence of hemolytic anemia (Petri 2012 Table 3).
- biopsy_lupus_nephritis with ANA or anti-dsDNA classifies without four criteria. The renal clinical item is proteinuria ≥500 mg/24 h or red blood cell casts, not the biopsy shortcut.

## Formula

```
SLICC 2012 SLE classification (Petri Table 3 + classification rule): 11 clinical flags (acute_cutaneous_lupus, chronic_cutaneous_lupus, oral_or_nasal_ulcers, nonscarring_alopecia, synovitis, serositis, renal, neurologic, hemolytic_anemia, leukopenia_or_lymphopenia, thrombocytopenia) and 6 immunologic flags (ana, anti_dsdna, anti_sm, antiphospholipid, low_complement, direct_coombs). clinical_count = count of clinical flags that are true. immunologic_count = count of immunologic flags that are true, except direct_coombs counts only when hemolytic_anemia is false. nephritis_shortcut iff biopsy_lupus_nephritis and (ana or anti_dsdna). classified iff nephritis_shortcut or (clinical_count ≥1 and immunologic_count ≥1 and clinical_count + immunologic_count ≥4). Criteria need not be concurrent. Not a diagnosis. Not 1997 ACR. Not 2019 EULAR/ACR
```

## Citation

[Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus](https://doi.org/10.1002/art.34473)
Petri M, Orbai AM, Alarcón GS, Gordon C, Merrill JT, Fortin PR, Bruce IN, Isenberg D, Wallace DJ, Nived O, Sturfelt G, Ramsey-Goldman R, Bae SC, Hanly JG, Sánchez-Guerrero J, Clarke A, Aranow C, Manzi S, Urowitz M, Gladman D, Kalunian K, Costner M, Werth VP, Zoma A, Bernatsky S, Ruiz-Irastorza G, Khamashta MA, Jacobsen S, Buyon JP, Maddison P, Dooley MA, van Vollenhoven RF, Ginzler E, Stoll T, Peschken C, Jorizzo JL, Callen JP, Lim SS, Fessler BJ, Inanc M, Kamen DL, Rahman A, Steinsson K, Franks AG, Sigler L, Hameed S, Fang H, Pham N, Brey R, Weisman MH, McGwin G, Magder LS
Arthritis Rheum. 2012;64(8):2677-2686
DOI: [10.1002/art.34473](https://doi.org/10.1002/art.34473)

## Worked example

### Three clinical and two immunologic criteria, classified

Given: `acute_cutaneous_lupus=true, ana=true, anti_dsdna=true, anti_sm=false, antiphospholipid=false, biopsy_lupus_nephritis=false, chronic_cutaneous_lupus=false, direct_coombs=false, hemolytic_anemia=false, leukopenia_or_lymphopenia=false, low_complement=false, neurologic=false, nonscarring_alopecia=false, oral_or_nasal_ulcers=true, renal=false, serositis=false, synovitis=true, thrombocytopenia=false`

1. acute_cutaneous_lupus, oral_or_nasal_ulcers, and synovitis true → clinical_count 3
2. ana and anti_dsdna true; remaining immunologic flags including direct_coombs false → immunologic_count 2
3. biopsy_lupus_nephritis false → nephritis_shortcut false; total 5 ≥4 with ≥1 clinical and ≥1 immunologic; classified true


### Biopsy lupus nephritis plus ANA, nephritis shortcut

Given: `acute_cutaneous_lupus=false, ana=true, anti_dsdna=false, anti_sm=false, antiphospholipid=false, biopsy_lupus_nephritis=true, chronic_cutaneous_lupus=false, direct_coombs=false, hemolytic_anemia=false, leukopenia_or_lymphopenia=false, low_complement=false, neurologic=false, nonscarring_alopecia=false, oral_or_nasal_ulcers=false, renal=false, serositis=false, synovitis=false, thrombocytopenia=false`

1. biopsy_lupus_nephritis true and ana true; anti_dsdna false
2. clinical_count 0; immunologic_count 1; four-criteria rule not met
3. nephritis_shortcut true; classified true


### All flags false, not classified

Given: `acute_cutaneous_lupus=false, ana=false, anti_dsdna=false, anti_sm=false, antiphospholipid=false, biopsy_lupus_nephritis=false, chronic_cutaneous_lupus=false, direct_coombs=false, hemolytic_anemia=false, leukopenia_or_lymphopenia=false, low_complement=false, neurologic=false, nonscarring_alopecia=false, oral_or_nasal_ulcers=false, renal=false, serositis=false, synovitis=false, thrombocytopenia=false`

1. All 11 clinical, 6 immunologic, and biopsy_lupus_nephritis false
2. clinical_count 0; immunologic_count 0; nephritis_shortcut false; classified false


### Biopsy lupus nephritis without ANA or anti-dsDNA, not classified

Given: `acute_cutaneous_lupus=false, ana=false, anti_dsdna=false, anti_sm=false, antiphospholipid=false, biopsy_lupus_nephritis=true, chronic_cutaneous_lupus=false, direct_coombs=false, hemolytic_anemia=false, leukopenia_or_lymphopenia=false, low_complement=false, neurologic=false, nonscarring_alopecia=false, oral_or_nasal_ulcers=false, renal=false, serositis=false, synovitis=false, thrombocytopenia=false`

1. biopsy_lupus_nephritis true; ana and anti_dsdna false; remaining flags false
2. nephritis_shortcut false (needs ANA or anti-dsDNA); four-criteria rule not met; classified false


### Four clinical criteria and zero immunologic, not classified

Given: `acute_cutaneous_lupus=true, ana=false, anti_dsdna=false, anti_sm=false, antiphospholipid=false, biopsy_lupus_nephritis=false, chronic_cutaneous_lupus=true, direct_coombs=false, hemolytic_anemia=false, leukopenia_or_lymphopenia=false, low_complement=false, neurologic=false, nonscarring_alopecia=false, oral_or_nasal_ulcers=true, renal=false, serositis=false, synovitis=true, thrombocytopenia=false`

1. acute_cutaneous_lupus, chronic_cutaneous_lupus, oral_or_nasal_ulcers, and synovitis true
2. All immunologic flags and biopsy_lupus_nephritis false → immunologic_count 0
3. clinical_count 4; nephritis_shortcut false; classified false (need ≥1 immunologic)


## Also searched as

- SLICC SLE classification criteria
- Petri 2012 lupus classification
- Systemic Lupus International Collaborating Clinics
- SLE classification not 1997 ACR
- not 2019 EULAR/ACR SLE
- lupus nephritis ANA anti-dsDNA
- immunologic clinical SLE criteria

## Parameters

- `acute_cutaneous_lupus` (boolean, required): Acute cutaneous lupus as assigned by the caller (Petri 2012 Table 3): lupus malar rash (do not count if malar discoid), bullous lupus, toxic epidermal necrolysis variant of SLE, maculopapular lupus rash, photosensitive lupus rash in the absence of dermatomyositis, or subacute cutaneous lupus. true or false. magent does not examine skin.
- `chronic_cutaneous_lupus` (boolean, required): Chronic cutaneous lupus as assigned by the caller (Petri 2012 Table 3): classic discoid (localized or generalized), hypertrophic (verrucous) lupus, lupus panniculitis (profundus), mucosal lupus, lupus erythematosus tumidus, chilblains lupus, or discoid lupus/lichen planus overlap. true or false. magent does not examine skin.
- `oral_or_nasal_ulcers` (boolean, required): Oral ulcers (palate, buccal, tongue) or nasal ulcers, in the absence of other causes, as assigned by the caller (Petri 2012 Table 3). true or false. magent does not examine mucosa.
- `nonscarring_alopecia` (boolean, required): Nonscarring alopecia: diffuse thinning or hair fragility with visible broken hairs, in the absence of other causes, as assigned by the caller (Petri 2012 Table 3). true or false. magent does not examine the scalp.
- `synovitis` (boolean, required): Synovitis involving 2 or more joints, characterized by swelling or effusion, or tenderness in 2 or more joints and at least 30 minutes of morning stiffness, as assigned by the caller (Petri 2012 Table 3). true or false. magent does not examine joints.
- `serositis` (boolean, required): Serositis as assigned by the caller (Petri 2012 Table 3): typical pleurisy >1 day or pleural effusion or pleural rub, or typical pericardial pain >1 day or pericardial effusion or pericardial rub or pericarditis by electrocardiography, in the absence of other causes. true or false. magent does not examine the chest.
- `renal` (boolean, required): Renal clinical criterion as assigned by the caller (Petri 2012 Table 3): urine protein-to-creatinine ratio (or 24-hour urine protein) representing 500 mg protein/24 hours, or red blood cell casts. Distinct from biopsy_lupus_nephritis. true or false. magent does not assay urine.
- `neurologic` (boolean, required): Neurologic criterion as assigned by the caller (Petri 2012 Table 3): seizures, psychosis, mononeuritis multiplex, myelitis, peripheral or cranial neuropathy, or acute confusional state, in the absence of other known causes. true or false. magent does not examine the nervous system.
- `hemolytic_anemia` (boolean, required): Hemolytic anemia as assigned by the caller (Petri 2012 Table 3). When true, direct_coombs does not count toward immunologic_count. true or false. magent does not assay hemolysis.
- `leukopenia_or_lymphopenia` (boolean, required): Leukopenia (<4,000/mm³ at least once) in the absence of other known causes, or lymphopenia (<1,000/mm³ at least once) in the absence of other known causes, as assigned by the caller (Petri 2012 Table 3). true or false. magent does not assay blood counts.
- `thrombocytopenia` (boolean, required): Thrombocytopenia (<100,000/mm³) at least once in the absence of other known causes, as assigned by the caller (Petri 2012 Table 3). true or false. magent does not assay platelets.
- `ana` (boolean, required): ANA above laboratory reference range as assigned by the caller (Petri 2012 Table 3). With biopsy_lupus_nephritis (or anti_dsdna), fulfills the nephritis shortcut. true or false. magent does not assay ANA.
- `anti_dsdna` (boolean, required): Anti-dsDNA above laboratory reference range (or >2-fold the reference range if tested by ELISA), as assigned by the caller (Petri 2012 Table 3). true or false. magent does not assay anti-dsDNA.
- `anti_sm` (boolean, required): Antibody to Sm nuclear antigen as assigned by the caller (Petri 2012 Table 3). true or false. magent does not assay anti-Sm.
- `antiphospholipid` (boolean, required): Antiphospholipid antibody positivity as assigned by the caller (Petri 2012 Table 3): lupus anticoagulant, false-positive rapid plasma reagin, medium- or high-titer anticardiolipin (IgA, IgG, or IgM), or anti-β2-glycoprotein I (IgA, IgG, or IgM). true or false. magent does not assay antiphospholipid antibodies.
- `low_complement` (boolean, required): Low C3, low C4, or low CH50 as assigned by the caller (Petri 2012 Table 3). true or false. magent does not assay complement.
- `direct_coombs` (boolean, required): Direct Coombs’ test as assigned by the caller (Petri 2012 Table 3). Counts toward immunologic_count only when hemolytic_anemia is false. true or false. magent does not run a Coombs test.
- `biopsy_lupus_nephritis` (boolean, required): Biopsy-proven nephritis compatible with SLE as assigned by the caller (Petri 2012 classification rule). With ANA or anti-dsDNA, classifies without four criteria. Distinct from the renal clinical item. true or false. magent does not read a biopsy.

## Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

Method: `POST /api/calc/slicc_sle`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: PREVIEW

- 1 to 25 items. Each item uses the same keys as the GET query parameters.
- POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
- The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
- HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
- Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
- x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request:

```json
{
  "items": [
    {
      "acute_cutaneous_lupus": "true",
      "ana": "true",
      "anti_dsdna": "true",
      "anti_sm": "false",
      "antiphospholipid": "false",
      "biopsy_lupus_nephritis": "false",
      "chronic_cutaneous_lupus": "false",
      "direct_coombs": "false",
      "hemolytic_anemia": "false",
      "leukopenia_or_lymphopenia": "false",
      "low_complement": "false",
      "neurologic": "false",
      "nonscarring_alopecia": "false",
      "oral_or_nasal_ulcers": "true",
      "renal": "false",
      "serositis": "false",
      "synovitis": "true",
      "thrombocytopenia": "false"
    },
    {
      "acute_cutaneous_lupus": "true",
      "ana": "true",
      "anti_dsdna": "true",
      "anti_sm": "false",
      "antiphospholipid": "false",
      "biopsy_lupus_nephritis": "false",
      "chronic_cutaneous_lupus": "false",
      "direct_coombs": "false",
      "hemolytic_anemia": "false",
      "leukopenia_or_lymphopenia": "false",
      "low_complement": "false",
      "neurologic": "false",
      "nonscarring_alopecia": "false",
      "oral_or_nasal_ulcers": "true",
      "renal": "false",
      "serositis": "false",
      "synovitis": "true",
      "thrombocytopenia": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/slicc-sle

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/slicc_sle",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Petri M, Orbai AM, Alarcón GS, Gordon C, Merrill JT, Fortin PR, Bruce IN, Isenberg D, Wallace DJ, Nived O, Sturfelt G, Ramsey-Goldman R, Bae SC, Hanly JG, Sánchez-Guerrero J, Clarke A, Aranow C, Manzi S, Urowitz M, Gladman D, Kalunian K, Costner M, Werth VP, Zoma A, Bernatsky S, Ruiz-Irastorza G, Khamashta MA, Jacobsen S, Buyon JP, Maddison P, Dooley MA, van Vollenhoven RF, Ginzler E, Stoll T, Peschken C, Jorizzo JL, Callen JP, Lim SS, Fessler BJ, Inanc M, Kamen DL, Rahman A, Steinsson K, Franks AG, Sigler L, Hameed S, Fang H, Pham N, Brey R, Weisman MH, McGwin G, Magder LS",
        "doi": "10.1002/art.34473",
        "id": "petri-2012",
        "pmid": "22553077",
        "source": "Arthritis Rheum. 2012;64(8):2677-2686",
        "title": "Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus"
      },
      "formula": "slicc_sle",
      "formula_expression": "SLICC 2012 SLE classification (Petri Table 3 + classification rule): 11 clinical flags (acute_cutaneous_lupus, chronic_cutaneous_lupus, oral_or_nasal_ulcers, nonscarring_alopecia, synovitis, serositis, renal, neurologic, hemolytic_anemia, leukopenia_or_lymphopenia, thrombocytopenia) and 6 immunologic flags (ana, anti_dsdna, anti_sm, antiphospholipid, low_complement, direct_coombs). clinical_count = count of clinical flags that are true. immunologic_count = count of immunologic flags that are true, except direct_coombs counts only when hemolytic_anemia is false. nephritis_shortcut iff biopsy_lupus_nephritis and (ana or anti_dsdna). classified iff nephritis_shortcut or (clinical_count ≥1 and immunologic_count ≥1 and clinical_count + immunologic_count ≥4). Criteria need not be concurrent. Not a diagnosis. Not 1997 ACR. Not 2019 EULAR/ACR",
      "classified": true,
      "clinical_count": 3,
      "immunologic_count": 2,
      "nephritis_shortcut": false
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Petri M, Orbai AM, Alarcón GS, Gordon C, Merrill JT, Fortin PR, Bruce IN, Isenberg D, Wallace DJ, Nived O, Sturfelt G, Ramsey-Goldman R, Bae SC, Hanly JG, Sánchez-Guerrero J, Clarke A, Aranow C, Manzi S, Urowitz M, Gladman D, Kalunian K, Costner M, Werth VP, Zoma A, Bernatsky S, Ruiz-Irastorza G, Khamashta MA, Jacobsen S, Buyon JP, Maddison P, Dooley MA, van Vollenhoven RF, Ginzler E, Stoll T, Peschken C, Jorizzo JL, Callen JP, Lim SS, Fessler BJ, Inanc M, Kamen DL, Rahman A, Steinsson K, Franks AG, Sigler L, Hameed S, Fang H, Pham N, Brey R, Weisman MH, McGwin G, Magder LS",
        "doi": "10.1002/art.34473",
        "id": "petri-2012",
        "pmid": "22553077",
        "source": "Arthritis Rheum. 2012;64(8):2677-2686",
        "title": "Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus"
      },
      "formula": "slicc_sle",
      "formula_expression": "SLICC 2012 SLE classification (Petri Table 3 + classification rule): 11 clinical flags (acute_cutaneous_lupus, chronic_cutaneous_lupus, oral_or_nasal_ulcers, nonscarring_alopecia, synovitis, serositis, renal, neurologic, hemolytic_anemia, leukopenia_or_lymphopenia, thrombocytopenia) and 6 immunologic flags (ana, anti_dsdna, anti_sm, antiphospholipid, low_complement, direct_coombs). clinical_count = count of clinical flags that are true. immunologic_count = count of immunologic flags that are true, except direct_coombs counts only when hemolytic_anemia is false. nephritis_shortcut iff biopsy_lupus_nephritis and (ana or anti_dsdna). classified iff nephritis_shortcut or (clinical_count ≥1 and immunologic_count ≥1 and clinical_count + immunologic_count ≥4). Criteria need not be concurrent. Not a diagnosis. Not 1997 ACR. Not 2019 EULAR/ACR",
      "classified": true,
      "clinical_count": 3,
      "immunologic_count": 2,
      "nephritis_shortcut": false
    }
  ]
}
```

## Response fields

- `formula` (string): slicc_sle
- `formula_expression` (string): Petri 2012 SLICC SLE classification expression (Table 3 + classification rule)
- `classified` (boolean): true iff nephritis_shortcut or (clinical_count ≥1 and immunologic_count ≥1 and clinical_count + immunologic_count ≥4). Classification criteria for research, not a diagnosis of SLE. Not 1997 ACR. Not 2019 EULAR/ACR.
- `clinical_count` (integer): Count of the 11 Petri 2012 clinical criteria that are true.
- `immunologic_count` (integer): Count of the 6 Petri 2012 immunologic criteria that are true. direct_coombs is included only when hemolytic_anemia is false.
- `nephritis_shortcut` (boolean): true iff biopsy_lupus_nephritis and (ana or anti_dsdna) (Petri 2012 classification rule)
- `citation` (object): Petri 2012 Arthritis Rheum citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Petri M, Orbai AM, Alarcón GS, Gordon C, Merrill JT, Fortin PR, Bruce IN, Isenberg D, Wallace DJ, Nived O, Sturfelt G, Ramsey-Goldman R, Bae SC, Hanly JG, Sánchez-Guerrero J, Clarke A, Aranow C, Manzi S, Urowitz M, Gladman D, Kalunian K, Costner M, Werth VP, Zoma A, Bernatsky S, Ruiz-Irastorza G, Khamashta MA, Jacobsen S, Buyon JP, Maddison P, Dooley MA, van Vollenhoven RF, Ginzler E, Stoll T, Peschken C, Jorizzo JL, Callen JP, Lim SS, Fessler BJ, Inanc M, Kamen DL, Rahman A, Steinsson K, Franks AG, Sigler L, Hameed S, Fang H, Pham N, Brey R, Weisman MH, McGwin G, Magder LS",
    "doi": "10.1002/art.34473",
    "id": "petri-2012",
    "pmid": "22553077",
    "source": "Arthritis Rheum. 2012;64(8):2677-2686",
    "title": "Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus"
  },
  "formula": "slicc_sle",
  "formula_expression": "SLICC 2012 SLE classification (Petri Table 3 + classification rule): 11 clinical flags (acute_cutaneous_lupus, chronic_cutaneous_lupus, oral_or_nasal_ulcers, nonscarring_alopecia, synovitis, serositis, renal, neurologic, hemolytic_anemia, leukopenia_or_lymphopenia, thrombocytopenia) and 6 immunologic flags (ana, anti_dsdna, anti_sm, antiphospholipid, low_complement, direct_coombs). clinical_count = count of clinical flags that are true. immunologic_count = count of immunologic flags that are true, except direct_coombs counts only when hemolytic_anemia is false. nephritis_shortcut iff biopsy_lupus_nephritis and (ana or anti_dsdna). classified iff nephritis_shortcut or (clinical_count ≥1 and immunologic_count ≥1 and clinical_count + immunologic_count ≥4). Criteria need not be concurrent. Not a diagnosis. Not 1997 ACR. Not 2019 EULAR/ACR",
  "classified": true,
  "clinical_count": 3,
  "immunologic_count": 2,
  "nephritis_shortcut": false
}
```

## Errors

- HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged.
- HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
- HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
- HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged.

Shared HTTP 402 and 503: https://magentlab.com/docs/payments

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- [ACR/EULAR PMR](https://magentlab.com/docs/acr-eular-pmr) — Apply the 2012 EULAR/ACR polymyalgia rheumatica classification criteria (Dasgupta Table 4): require age ≥50, bilateral shoulder aching, and abnormal CRP and/or ESR, then return the clinical score with or without optional ultrasound and whether the published cut point classifies PMR. Not a PMR diagnosis.
- [ACR/EULAR Sjögren](https://magentlab.com/docs/acr-eular-sjogren) — Apply the 2016 ACR/EULAR classification criteria for primary Sjögren's syndrome (Shiboski Table 3): require published inclusion and no exclusion, then return the five-item weighted score and whether the ≥4 cut point classifies primary Sjögren's syndrome. Not a diagnosis.

## Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s.

- GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall).
- HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote.
- Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional.
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402.

- offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront.
- offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization.

- not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search.

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers).

Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments

Stdio MCP (one process per host): https://magentlab.com/docs/mcp

## Guarantees

- HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
- exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
- HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
- Execution is timeout-bounded and concurrency-capped.
- Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.