# Levy 2006 Seattle Heart Failure Model Seattle Heart Failure Model Status: LIVE Price: $0.005 USDC `GET /api/calc/shfm` HTML: https://magentlab.com/docs/seattle-hf Markdown: https://magentlab.com/docs/seattle-hf.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Compute Levy 2006 Seattle Heart Failure Model 1-, 2-, and 3-year survival percents from Table 2 multivariate hazard ratios for a patient already on the listed medications and devices. ## When to use When an agent already has those Levy 2006 predictors and needs that paper's 1-, 2-, and 3-year survival percents. Caller assigns NYHA class, etiology, and therapy flags. Not a diagnosis, prescription, or device order. ## When not to use - Not a medical device. Not a diagnosis of heart failure. Not a treatment order, medication recommendation, or device order. - Estimates 1-, 2-, and 3-year survival from Levy 2006 Table 2 for a patient already on the listed medications and devices. Does not estimate whether a drug or device can be added safely and is not a reason to withhold therapy. - Caller assigns NYHA class, ischemic etiology, and medication/device flags. magent does not examine the patient, does not measure blood pressure or weight, and does not assay labs. - Diuretic dose is furosemide-equivalent mg/kg/day (paper: furosemide 80 = torsemide 40 = bumetanide 3). Lymphocytes >47%, uric acid <3.4 mg/dL, and SBP >160 mm Hg are truncated as in the paper. Gender male 1.089 was forced into Table 2. - Derived and validated mainly in systolic heart-failure outpatients. Not for hospitalized patients or major non-cardiac comorbidities. Does not include peak VO2 or natriuretic peptides. ## Formula ``` score = sum(ln(HR)*x); S(t)=exp(-0.0405*t)**exp(score) for t years 0-5; Levy 2006 Table 2 multivariate HRs (italic β=ln(HR); medication/device = patient-already-on column); 1/2/3-year survival % round 1 decimal; age/10 * ln(1.090); male ln(1.089) (forced); NYHA * ln(1.600); (100/EF)*ln(1.030); ischemic ln(1.354); min(SBP,160)/10 * ln(0.877); furosemide-eq mg/kg/day * ln(1.178) (furosemide 80 = torsemide 40 = bumetanide 3); allopurinol ln(1.571); if Na<138: (138-Na)*ln(1.050); (100/cholesterol)*ln(2.206); if Hb<16: (16-Hb)*ln(1.124); if Hb>16: (Hb-16)*ln(1.336); min(%lymphocytes,47)/5 * ln(0.897); max(uric_acid,3.4)*ln(1.064); ACEI ln(0.77); beta-blocker ln(0.66); ARB ln(0.85); K-sparing diuretic ln(0.74); statin ln(0.63); BiV pacemaker ln(1.00); ICD ln(0.73); BiV-ICD ln(0.79); devices mutually exclusive; not a diagnosis or treatment/device order ``` ## Citation [The Seattle Heart Failure Model: Prediction of Survival in Heart Failure](https://doi.org/10.1161/CIRCULATIONAHA.105.584102) Levy WC, Mozaffarian D, Linker DT, Sutradhar SC, Anker SD, Cropp AB, et al. Circulation. 2006;113(11):1424-1433 DOI: [10.1161/CIRCULATIONAHA.105.584102](https://doi.org/10.1161/CIRCULATIONAHA.105.584102) ## Worked example ### NYHA II, EF 30%, male age 60, SBP 120, no diuretic, ACE inhibitor and beta-blocker Given: `ace_inhibitor=true, age=60, allopurinol=false, arb=false, beta_blocker=true, biv_icd=false, biv_pacemaker=false, ef_percent=30, hemoglobin_g_dl=14, icd=false, ischemic=false, k_sparing_diuretic=false, loop_diuretic_furosemide_eq_mg_day=0, lymphocyte_percent=25, nyha=2, sbp_mm_hg=120, sex=male, sodium_meq_l=140, statin=false, total_cholesterol_mg_dl=180, uric_acid_mg_dl=6, weight_kg=80` 1. Table 2 score = ln(1.090)*(60/10) + ln(1.089) + ln(1.600)*2 + ln(1.030)*(100/30) + ln(0.877)*(120/10) + ln(2.206)*(100/180) + ln(1.124)*(16-14) + ln(0.897)*(25/5) + ln(1.064)*6 + ln(0.77) + ln(0.66) 2. ischemic, allopurinol, ARB, K-sparing diuretic, statin, and devices are false (0); Na 140 ≥138 adds 0; diuretic 0 mg/kg/day 3. score -0.1089 4. S(t)=exp(-0.0405*t)**exp(score); survival_1y_percent 96.4; survival_2y_percent 93.0; survival_3y_percent 89.7 ## Also searched as - Seattle Heart Failure Model - SHFM survival - Levy 2006 heart failure survival - PRAISE1 heart failure model - NYHA EF diuretic survival - 1-year heart failure survival - furosemide equivalent heart failure ## Parameters - `age` (integer, required): Age in years (integer 14-100). Levy 2006 Table 2: per decade, multivariate HR 1.090. magent does not take a date of birth. - `sex` (string, required): Sex used by the forced Table 2 male HR 1.089 (female or male). magent does not assign sex. - `nyha` (integer, required): NYHA class 1-4 as assigned by the caller (integer). Levy 2006 Table 2 multivariate HR 1.600 per class. magent does not examine the patient. - `ef_percent` (number, required): Left-ventricular ejection fraction in percent (1-80). Enters as 100/EF with Table 2 HR 1.030. magent does not interpret an echocardiogram. - `ischemic` (boolean, required): Ischemic etiology as assigned by the caller (true or false). Table 2 multivariate HR 1.354. magent does not assign etiology. - `sbp_mm_hg` (number, required): Systolic blood pressure in mm Hg (50-250). Table 2: per 10 mm Hg, HR 0.877, truncated at 160 (SBP 180 is scored as 160). magent does not measure blood pressure. - `weight_kg` (number, required): Body weight in kg (20-250) used only to convert the furosemide-equivalent diuretic dose to mg/kg/day. magent does not weigh the patient. - `loop_diuretic_furosemide_eq_mg_day` (number, required): Daily loop-diuretic dose as furosemide milligram equivalent (0-1000). Paper conversion: furosemide 80 = torsemide 40 = bumetanide 3. Divided by weight_kg; Table 2 HR 1.178 per mg/kg/day. magent does not prescribe a diuretic. - `allopurinol` (boolean, required): Current allopurinol as assigned by the caller (true or false). Table 2 multivariate HR 1.571. magent does not prescribe allopurinol. - `sodium_meq_l` (number, required): Serum sodium in mEq/L (110-160). Table 2: if Na<138, (138-Na) with HR 1.050 per mEq; values ≥138 add 0. magent does not assay sodium. - `total_cholesterol_mg_dl` (number, required): Total cholesterol in mg/dL (50-800). Enters as 100/cholesterol with Table 2 HR 2.206. magent does not assay lipids. - `hemoglobin_g_dl` (number, required): Hemoglobin in g/dL (4-22). Table 2: if Hb<16, (16-Hb) with HR 1.124 per g/dL; if Hb>16, (Hb-16) with HR 1.336 per g/dL. magent does not assay hemoglobin. - `lymphocyte_percent` (number, required): Percent lymphocytes (0-100). Table 2: per 5% when <47%, HR 0.897; values >47% are truncated to 47. magent does not assay a CBC. - `uric_acid_mg_dl` (number, required): Serum uric acid in mg/dL (0.5-25). Table 2: per mg/dL when >3.4, HR 1.064; values <3.4 are truncated to 3.4. magent does not assay uric acid. - `ace_inhibitor` (boolean, required): Patient already on an ACE inhibitor as assigned by the caller (true or false). Table 2 already-on HR 0.77. Not a prescription. - `beta_blocker` (boolean, required): Patient already on a beta-blocker as assigned by the caller (true or false). Table 2 already-on HR 0.66. Not a prescription. - `arb` (boolean, required): Patient already on an angiotensin-receptor blocker as assigned by the caller (true or false). Table 2 already-on HR 0.85. Not a prescription. - `k_sparing_diuretic` (boolean, required): Patient already on a potassium-sparing diuretic as assigned by the caller (true or false). Table 2 already-on HR 0.74. Not a prescription. - `statin` (boolean, required): Patient already on a statin as assigned by the caller (true or false). Table 2 already-on / multivariate HR 0.63. Not a prescription. - `biv_pacemaker` (boolean, required): Patient already has a biventricular pacemaker (without ICD) as assigned by the caller (true or false). Table 2 already-on HR 1.00. Mutually exclusive with icd and biv_icd. Not a device order. - `icd` (boolean, required): Patient already has an ICD (without biventricular pacing) as assigned by the caller (true or false). Table 2 already-on HR 0.73. Mutually exclusive with biv_pacemaker and biv_icd. Not a device order. - `biv_icd` (boolean, required): Patient already has a biventricular ICD as assigned by the caller (true or false). Table 2 already-on HR 0.79. Mutually exclusive with biv_pacemaker and icd. Not a device order. ## 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/shfm` 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": [ { "ace_inhibitor": "true", "age": "60", "allopurinol": "false", "arb": "false", "beta_blocker": "true", "biv_icd": "false", "biv_pacemaker": "false", "ef_percent": "30", "hemoglobin_g_dl": "14", "icd": "false", "ischemic": "false", "k_sparing_diuretic": "false", "loop_diuretic_furosemide_eq_mg_day": "0", "lymphocyte_percent": "25", "nyha": "2", "sbp_mm_hg": "120", "sex": "male", "sodium_meq_l": "140", "statin": "false", "total_cholesterol_mg_dl": "180", "uric_acid_mg_dl": "6", "weight_kg": "80" }, { "ace_inhibitor": "true", "age": "60", "allopurinol": "false", "arb": "false", "beta_blocker": "true", "biv_icd": "false", "biv_pacemaker": "false", "ef_percent": "30", "hemoglobin_g_dl": "14", "icd": "false", "ischemic": "false", "k_sparing_diuretic": "false", "loop_diuretic_furosemide_eq_mg_day": "0", "lymphocyte_percent": "25", "nyha": "2", "sbp_mm_hg": "120", "sex": "male", "sodium_meq_l": "140", "statin": "false", "total_cholesterol_mg_dl": "180", "uric_acid_mg_dl": "6", "weight_kg": "80" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/seattle-hf Example 200: ```json { "count": 2, "path": "/api/calc/shfm", "items": [ { "age": 60, "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": "Levy WC, Mozaffarian D, Linker DT, Sutradhar SC, Anker SD, Cropp AB, et al.", "doi": "10.1161/CIRCULATIONAHA.105.584102", "id": "levy-2006-shfm", "pmid": "16534009", "source": "Circulation. 2006;113(11):1424-1433", "title": "The Seattle Heart Failure Model: Prediction of Survival in Heart Failure" }, "formula": "shfm", "formula_expression": "score = sum(ln(HR)*x); S(t)=exp(-0.0405*t)**exp(score) for t years 0-5; Levy 2006 Table 2 multivariate HRs (italic β=ln(HR); medication/device = patient-already-on column); 1/2/3-year survival % round 1 decimal; age/10 * ln(1.090); male ln(1.089) (forced); NYHA * ln(1.600); (100/EF)*ln(1.030); ischemic ln(1.354); min(SBP,160)/10 * ln(0.877); furosemide-eq mg/kg/day * ln(1.178) (furosemide 80 = torsemide 40 = bumetanide 3); allopurinol ln(1.571); if Na<138: (138-Na)*ln(1.050); (100/cholesterol)*ln(2.206); if Hb<16: (16-Hb)*ln(1.124); if Hb>16: (Hb-16)*ln(1.336); min(%lymphocytes,47)/5 * ln(0.897); max(uric_acid,3.4)*ln(1.064); ACEI ln(0.77); beta-blocker ln(0.66); ARB ln(0.85); K-sparing diuretic ln(0.74); statin ln(0.63); BiV pacemaker ln(1.00); ICD ln(0.73); BiV-ICD ln(0.79); devices mutually exclusive; not a diagnosis or treatment/device order", "score": -0.1089, "lymphocyte_percent": 25.0, "weight_kg": 80.0, "sex": "male", "sbp_mm_hg": 120.0, "total_cholesterol_mg_dl": 180.0, "hemoglobin_g_dl": 14.0, "nyha": 2, "beta_blocker": true, "ef_percent": 30.0, "statin": false, "ace_inhibitor": true, "allopurinol": false, "arb": false, "biv_icd": false, "biv_pacemaker": false, "diuretic_furosemide_eq_mg_kg_day": 0.0, "icd": false, "ischemic": false, "k_sparing_diuretic": false, "loop_diuretic_furosemide_eq_mg_day": 0.0, "sodium_meq_l": 140.0, "survival_1y_percent": 96.4, "survival_2y_percent": 93.0, "survival_3y_percent": 89.7, "uric_acid_mg_dl": 6.0 }, { "age": 60, "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": "Levy WC, Mozaffarian D, Linker DT, Sutradhar SC, Anker SD, Cropp AB, et al.", "doi": "10.1161/CIRCULATIONAHA.105.584102", "id": "levy-2006-shfm", "pmid": "16534009", "source": "Circulation. 2006;113(11):1424-1433", "title": "The Seattle Heart Failure Model: Prediction of Survival in Heart Failure" }, "formula": "shfm", "formula_expression": "score = sum(ln(HR)*x); S(t)=exp(-0.0405*t)**exp(score) for t years 0-5; Levy 2006 Table 2 multivariate HRs (italic β=ln(HR); medication/device = patient-already-on column); 1/2/3-year survival % round 1 decimal; age/10 * ln(1.090); male ln(1.089) (forced); NYHA * ln(1.600); (100/EF)*ln(1.030); ischemic ln(1.354); min(SBP,160)/10 * ln(0.877); furosemide-eq mg/kg/day * ln(1.178) (furosemide 80 = torsemide 40 = bumetanide 3); allopurinol ln(1.571); if Na<138: (138-Na)*ln(1.050); (100/cholesterol)*ln(2.206); if Hb<16: (16-Hb)*ln(1.124); if Hb>16: (Hb-16)*ln(1.336); min(%lymphocytes,47)/5 * ln(0.897); max(uric_acid,3.4)*ln(1.064); ACEI ln(0.77); beta-blocker ln(0.66); ARB ln(0.85); K-sparing diuretic ln(0.74); statin ln(0.63); BiV pacemaker ln(1.00); ICD ln(0.73); BiV-ICD ln(0.79); devices mutually exclusive; not a diagnosis or treatment/device order", "score": -0.1089, "lymphocyte_percent": 25.0, "weight_kg": 80.0, "sex": "male", "sbp_mm_hg": 120.0, "total_cholesterol_mg_dl": 180.0, "hemoglobin_g_dl": 14.0, "nyha": 2, "beta_blocker": true, "ef_percent": 30.0, "statin": false, "ace_inhibitor": true, "allopurinol": false, "arb": false, "biv_icd": false, "biv_pacemaker": false, "diuretic_furosemide_eq_mg_kg_day": 0.0, "icd": false, "ischemic": false, "k_sparing_diuretic": false, "loop_diuretic_furosemide_eq_mg_day": 0.0, "sodium_meq_l": 140.0, "survival_1y_percent": 96.4, "survival_2y_percent": 93.0, "survival_3y_percent": 89.7, "uric_acid_mg_dl": 6.0 } ] } ``` ## Response fields - `formula` (string): shfm - `formula_expression` (string): Levy 2006 Table 2 multivariate SHFM score and S(t) - `age` (integer): Age in years used (14-100) - `sex` (string): female or male used - `nyha` (integer): NYHA class 1-4 used - `ef_percent` (number): Ejection fraction used, percent - `ischemic` (boolean): Caller-assigned ischemic etiology used - `sbp_mm_hg` (number): Systolic BP used, mm Hg - `weight_kg` (number): Weight used, kg - `loop_diuretic_furosemide_eq_mg_day` (number): Furosemide-equivalent loop-diuretic dose used, mg/day - `diuretic_furosemide_eq_mg_kg_day` (number): Table 2 diuretic dose, furosemide-eq mg/kg/day, 4 decimals - `allopurinol` (boolean): Caller-assigned allopurinol used - `sodium_meq_l` (number): Serum sodium used, mEq/L - `total_cholesterol_mg_dl` (number): Total cholesterol used, mg/dL - `hemoglobin_g_dl` (number): Hemoglobin used, g/dL - `lymphocyte_percent` (number): Percent lymphocytes used - `uric_acid_mg_dl` (number): Uric acid used, mg/dL - `ace_inhibitor` (boolean): Caller-assigned already-on ACE inhibitor used - `beta_blocker` (boolean): Caller-assigned already-on beta-blocker used - `arb` (boolean): Caller-assigned already-on ARB used - `k_sparing_diuretic` (boolean): Caller-assigned already-on potassium-sparing diuretic used - `statin` (boolean): Caller-assigned already-on statin used - `biv_pacemaker` (boolean): Caller-assigned already-on biventricular pacemaker used - `icd` (boolean): Caller-assigned already-on ICD used - `biv_icd` (boolean): Caller-assigned already-on biventricular ICD used - `score` (number): Table 2 SHFM score (sum of ln(HR)*x), 4 decimals - `survival_1y_percent` (number): 1-year survival percent, 1 decimal - `survival_2y_percent` (number): 2-year survival percent, 1 decimal - `survival_3y_percent` (number): 3-year survival percent, 1 decimal - `citation` (object): Levy et al. Circulation 2006 citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "age": 60, "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": "Levy WC, Mozaffarian D, Linker DT, Sutradhar SC, Anker SD, Cropp AB, et al.", "doi": "10.1161/CIRCULATIONAHA.105.584102", "id": "levy-2006-shfm", "pmid": "16534009", "source": "Circulation. 2006;113(11):1424-1433", "title": "The Seattle Heart Failure Model: Prediction of Survival in Heart Failure" }, "formula": "shfm", "formula_expression": "score = sum(ln(HR)*x); S(t)=exp(-0.0405*t)**exp(score) for t years 0-5; Levy 2006 Table 2 multivariate HRs (italic β=ln(HR); medication/device = patient-already-on column); 1/2/3-year survival % round 1 decimal; age/10 * ln(1.090); male ln(1.089) (forced); NYHA * ln(1.600); (100/EF)*ln(1.030); ischemic ln(1.354); min(SBP,160)/10 * ln(0.877); furosemide-eq mg/kg/day * ln(1.178) (furosemide 80 = torsemide 40 = bumetanide 3); allopurinol ln(1.571); if Na<138: (138-Na)*ln(1.050); (100/cholesterol)*ln(2.206); if Hb<16: (16-Hb)*ln(1.124); if Hb>16: (Hb-16)*ln(1.336); min(%lymphocytes,47)/5 * ln(0.897); max(uric_acid,3.4)*ln(1.064); ACEI ln(0.77); beta-blocker ln(0.66); ARB ln(0.85); K-sparing diuretic ln(0.74); statin ln(0.63); BiV pacemaker ln(1.00); ICD ln(0.73); BiV-ICD ln(0.79); devices mutually exclusive; not a diagnosis or treatment/device order", "score": -0.1089, "lymphocyte_percent": 25.0, "weight_kg": 80.0, "sex": "male", "sbp_mm_hg": 120.0, "total_cholesterol_mg_dl": 180.0, "hemoglobin_g_dl": 14.0, "nyha": 2, "beta_blocker": true, "ef_percent": 30.0, "statin": false, "ace_inhibitor": true, "allopurinol": false, "arb": false, "biv_icd": false, "biv_pacemaker": false, "diuretic_furosemide_eq_mg_kg_day": 0.0, "icd": false, "ischemic": false, "k_sparing_diuretic": false, "loop_diuretic_furosemide_eq_mg_day": 0.0, "sodium_meq_l": 140.0, "survival_1y_percent": 96.4, "survival_2y_percent": 93.0, "survival_3y_percent": 89.7, "uric_acid_mg_dl": 6.0 } ``` ## Errors - HTTP 400 `invalid_shfm`: Seattle Heart Failure Model inputs must match Levy 2006 Table 2 clinical, laboratory, medication, and device predictors. 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 ## Related tools - [MAGGIC](https://magentlab.com/docs/maggic) — Sum the Pocock 2013 MAGGIC integer chart from thirteen caller-supplied heart-failure predictors and return the published Table 4 1-year and 3-year death probabilities for scores 0-50. - [GWTG-HF](https://magentlab.com/docs/gwtg-hf) — Sum Peterson 2010 Figure 2 GWTG-HF integer points from seven admission predictors (age, systolic BP, BUN, sodium, heart rate, COPD, and caller-assigned nonblack race) for in-hospital mortality in hospitalized heart failure. - [PCP-HF 10-year incident HF](https://magentlab.com/docs/pcp-hf) — Compute the Khan 2019 PCP-HF 10-year incident heart-failure percent for adults aged 30-79 from Table 2 sex- and cohort-specific Cox coefficients. ## 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.