{"id":"sentinel-values","title":"Placeholder values hiding as data: caller-declared sentinels and likely candidates","description":"Scans columns of values for sentinels. Values you declare in a dictionary (for example -1 means unknown in column age) are reported as asserted hits with their row paths. Other values that look like missing-data markers are reported separately as candidates, never asserted: the pandas default NA strings, spreadsheet error values, whitespace-only text, placeholder words, zero and epoch dates, fixed-width integer limits, -1 in an otherwise non-negative column, runs of 9s above or below every other value, and a numeric value repeated at least 3 times that lies beyond 3 interquartile ranges of the rest. For agents about to average, sum, join or load a column. It cannot know what a value means: a candidate may be real data, and 0 is never flagged.","roi":"Sentinels silently distort means, joins and date ranges. 20,000 values per $0.005 call.","audience":"developer","package":"data-contract-kit","channels":["x402","mcp"],"endpoint":{"method":"POST","url":"https://agents.writerslogic.com/api/v1/sentinel-values","path":"/api/v1/sentinel-values","contentType":"application/json"},"price":{"amount":"0.005","currency":"USDC","network":"base","perCall":true,"failedCallsCharged":false},"inputSchema":{"type":"object","additionalProperties":false,"required":["columns"],"properties":{"columns":{"type":"array","minItems":1,"maxItems":50,"items":{"type":"object","additionalProperties":false,"required":["name","values"],"properties":{"name":{"type":"string","maxLength":100},"values":{"type":"array","maxItems":2000,"items":{"description":"A cell: string, number, boolean or null."}}}}},"dictionary":{"type":"array","maxItems":100,"items":{"type":"object","additionalProperties":false,"required":["value"],"properties":{"column":{"type":"string","maxLength":100,"description":"Limit the entry to this column; omit for all columns."},"value":{"description":"The sentinel value (string, number or boolean); matched by type and value."},"meaning":{"type":"string","maxLength":200}}},"description":"Values you know are sentinels."}}},"resultSchema":{"type":"object","properties":{"status":{"type":"string","enum":["pass","fail","unknown","unsupported"],"description":"pass: every rule held. fail: a rule was violated (see witnesses). unknown: the input lacks the evidence to decide. unsupported: outside what this engine covers. Missing evidence is never a pass."},"columns":{"type":"array","items":{"type":"object","properties":{"name":{"type":"string"},"valueCount":{"type":"integer"},"nullCount":{"type":"integer"},"assertedHits":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Dictionary value"},"meaning":{"anyOf":[{"type":"string"},{"type":"null"}]},"count":{"type":"integer"},"share":{"type":"number"},"firstIndexes":{"type":"array","items":{"type":"integer"}}}}},"candidates":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Candidate value"},"count":{"type":"integer"},"share":{"type":"number"},"asserted":{"type":"boolean","description":"Always false: candidates are never asserted."},"firstIndexes":{"type":"array","items":{"type":"integer"}},"reasons":{"type":"array","items":{"type":"object","properties":{"rule":{"type":"string"},"source":{"type":"string"},"kind":{"type":"string","enum":["documented","convention","arithmetic","statistical"]},"note":{"type":"string"}}}}}}}}}},"assertedHitCount":{"type":"integer"},"candidateCount":{"type":"integer"},"witnesses":{"type":"array","items":{"type":"object","properties":{"ruleId":{"type":"string"},"detail":{"type":"string"},"path":{"type":"string","description":"JSON pointer or dotted path into the input."},"offset":{"type":"integer"},"index":{"type":"integer"},"expected":{"description":"What the rule required."},"actual":{"description":"What the input had."}}}},"versions":{"type":"object","description":"Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile)."},"limits":{"type":"array","items":{"type":"string"}},"deterministic":{"type":"boolean","description":"Always true: pure code, no model."}}},"outputSchema":{"type":"object","properties":{"data":{"type":"object","properties":{"status":{"type":"string","enum":["pass","fail","unknown","unsupported"],"description":"pass: every rule held. fail: a rule was violated (see witnesses). unknown: the input lacks the evidence to decide. unsupported: outside what this engine covers. Missing evidence is never a pass."},"columns":{"type":"array","items":{"type":"object","properties":{"name":{"type":"string"},"valueCount":{"type":"integer"},"nullCount":{"type":"integer"},"assertedHits":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Dictionary value"},"meaning":{"anyOf":[{"type":"string"},{"type":"null"}]},"count":{"type":"integer"},"share":{"type":"number"},"firstIndexes":{"type":"array","items":{"type":"integer"}}}}},"candidates":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Candidate value"},"count":{"type":"integer"},"share":{"type":"number"},"asserted":{"type":"boolean","description":"Always false: candidates are never asserted."},"firstIndexes":{"type":"array","items":{"type":"integer"}},"reasons":{"type":"array","items":{"type":"object","properties":{"rule":{"type":"string"},"source":{"type":"string"},"kind":{"type":"string","enum":["documented","convention","arithmetic","statistical"]},"note":{"type":"string"}}}}}}}}}},"assertedHitCount":{"type":"integer"},"candidateCount":{"type":"integer"},"witnesses":{"type":"array","items":{"type":"object","properties":{"ruleId":{"type":"string"},"detail":{"type":"string"},"path":{"type":"string","description":"JSON pointer or dotted path into the input."},"offset":{"type":"integer"},"index":{"type":"integer"},"expected":{"description":"What the rule required."},"actual":{"description":"What the input had."}}}},"versions":{"type":"object","description":"Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile)."},"limits":{"type":"array","items":{"type":"string"}},"deterministic":{"type":"boolean","description":"Always true: pure code, no model."}}},"_provenance":{"type":"object","description":"C2PA-aligned manifest and W3C VC 2.0 (eddsa-jcs-2022) issued by the hub DID; verify at POST /api/v1/verify-provenance"}},"required":["data","_provenance"]},"example":{"columns":[{"name":"age","values":[34,29,-1,41,-1,52,38,27,45,33,30,36]},{"name":"joined","values":["2021-03-04","1970-01-01","2022-07-19","N/A"]}],"dictionary":[{"column":"age","value":-1,"meaning":"unknown"}]},"openapiOperation":{"operationId":"sentinel_values","summary":"Placeholder values hiding as data: caller-declared sentinels and likely candidates","description":"Scans columns of values for sentinels. Values you declare in a dictionary (for example -1 means unknown in column age) are reported as asserted hits with their row paths. Other values that look like missing-data markers are reported separately as candidates, never asserted: the pandas default NA strings, spreadsheet error values, whitespace-only text, placeholder words, zero and epoch dates, fixed-width integer limits, -1 in an otherwise non-negative column, runs of 9s above or below every other value, and a numeric value repeated at least 3 times that lies beyond 3 interquartile ranges of the rest. For agents about to average, sum, join or load a column. It cannot know what a value means: a candidate may be real data, and 0 is never flagged.\n\nPrice: 0.005 USDC on Base (x402).","x-x402-price-usdc":"0.005","x-x402-amount":"5000","x-payment-info":{"protocols":["x402"],"price":{"mode":"fixed","currency":"USD","amount":"0.005"}},"x-audience":"developer","x-sample-url":"https://agents.writerslogic.com/api/v1/samples/sentinel-values","security":[{"x402":[]},{"apiKey":[]}],"requestBody":{"required":true,"content":{"application/json":{"schema":{"type":"object","additionalProperties":false,"required":["columns"],"properties":{"columns":{"type":"array","minItems":1,"maxItems":50,"items":{"type":"object","additionalProperties":false,"required":["name","values"],"properties":{"name":{"type":"string","maxLength":100},"values":{"type":"array","maxItems":2000,"items":{"description":"A cell: string, number, boolean or null."}}}}},"dictionary":{"type":"array","maxItems":100,"items":{"type":"object","additionalProperties":false,"required":["value"],"properties":{"column":{"type":"string","maxLength":100,"description":"Limit the entry to this column; omit for all columns."},"value":{"description":"The sentinel value (string, number or boolean); matched by type and value."},"meaning":{"type":"string","maxLength":200}}},"description":"Values you know are sentinels."}}},"example":{"columns":[{"name":"age","values":[34,29,-1,41,-1,52,38,27,45,33,30,36]},{"name":"joined","values":["2021-03-04","1970-01-01","2022-07-19","N/A"]}],"dictionary":[{"column":"age","value":-1,"meaning":"unknown"}]}}}},"responses":{"200":{"description":"Paid result with provenance","content":{"application/json":{"schema":{"type":"object","properties":{"data":{"type":"object","properties":{"status":{"type":"string","enum":["pass","fail","unknown","unsupported"],"description":"pass: every rule held. fail: a rule was violated (see witnesses). unknown: the input lacks the evidence to decide. unsupported: outside what this engine covers. Missing evidence is never a pass."},"columns":{"type":"array","items":{"type":"object","properties":{"name":{"type":"string"},"valueCount":{"type":"integer"},"nullCount":{"type":"integer"},"assertedHits":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Dictionary value"},"meaning":{"anyOf":[{"type":"string"},{"type":"null"}]},"count":{"type":"integer"},"share":{"type":"number"},"firstIndexes":{"type":"array","items":{"type":"integer"}}}}},"candidates":{"type":"array","items":{"type":"object","properties":{"value":{"description":"Candidate value"},"count":{"type":"integer"},"share":{"type":"number"},"asserted":{"type":"boolean","description":"Always false: candidates are never asserted."},"firstIndexes":{"type":"array","items":{"type":"integer"}},"reasons":{"type":"array","items":{"type":"object","properties":{"rule":{"type":"string"},"source":{"type":"string"},"kind":{"type":"string","enum":["documented","convention","arithmetic","statistical"]},"note":{"type":"string"}}}}}}}}}},"assertedHitCount":{"type":"integer"},"candidateCount":{"type":"integer"},"witnesses":{"type":"array","items":{"type":"object","properties":{"ruleId":{"type":"string"},"detail":{"type":"string"},"path":{"type":"string","description":"JSON pointer or dotted path into the input."},"offset":{"type":"integer"},"index":{"type":"integer"},"expected":{"description":"What the rule required."},"actual":{"description":"What the input had."}}}},"versions":{"type":"object","description":"Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile)."},"limits":{"type":"array","items":{"type":"string"}},"deterministic":{"type":"boolean","description":"Always true: pure code, no model."}}},"_provenance":{"type":"object","description":"C2PA-aligned manifest and W3C VC 2.0 (eddsa-jcs-2022) issued by the hub DID; verify at POST /api/v1/verify-provenance"}},"required":["data","_provenance"]}}}},"400":{"description":"Invalid request (no payment consumed)","content":{"application/json":{"schema":{"type":"object","properties":{"error":{"type":"string"},"code":{"type":"string"}}}}}},"401":{"description":"Invalid X-API-KEY","content":{"application/json":{"schema":{"type":"object","properties":{"error":{"type":"string"},"code":{"type":"string"}}}}}},"402":{"description":"Payment required or invalid","content":{"application/json":{"schema":{"type":"object","description":"x402 v2 PaymentRequired (also base64 in the PAYMENT-REQUIRED header)","properties":{"x402Version":{"type":"integer"},"error":{"type":"string"},"code":{"type":"string"},"resource":{"type":"object"},"accepts":{"type":"array","items":{"type":"object"}},"extensions":{"type":"object"}}}}}},"502":{"description":"Upstream failure; the payment is released or not settled","content":{"application/json":{"schema":{"type":"object","properties":{"error":{"type":"string"},"code":{"type":"string"}}}}}}}},"links":{"docs":"https://agents.writerslogic.com/docs/sentinel-values/","docsJson":"https://agents.writerslogic.com/docs/sentinel-values.json","sample":"https://agents.writerslogic.com/api/v1/samples/sentinel-values","openapi":"https://agents.writerslogic.com/openapi.json","catalog":"https://agents.writerslogic.com/api/v1/catalog","verifyProvenance":"https://agents.writerslogic.com/api/v1/verify-provenance","index":"https://agents.writerslogic.com/docs/index.json"}}