{"uid":"cap_vs-BKMn9L81Dk_E0ynXBR","slug":"toolfit-by-youraitools-mcp-tool-change-detector-c522d2f0","name":"ToolFit by YourAITools – MCP Tool Change Detector","description":"AI agent tool change detector API (MCP tool diff). Compare an agent tool list now (tools array or public remote MCP URL) with a pin from an earlier ToolFit call (or a baseline array): removed or added tools, changed descriptions with a word diff and new poisoning findings, removed or newly required params, type and enum changes, annotation changes. Verdict: unchanged, compatible, review, suspicious or breaking.","url":"https://api.youraitools.co/toolfit/v1/diff?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":[],"properties":{"pin":{"type":"string","description":"A pin (set_id \"ts_...\" from an earlier ToolFit call) to compare against."},"url":{"type":"string","description":"Public remote MCP server URL (Streamable HTTP, https), e.g. https://api.youraitools.co/mcp/hub. ToolFit only lists its tools."},"tools":{"type":"array","items":{"type":"object"},"description":"Tool definitions: MCP tools/list entries, OpenAI {type:\"function\",function:{...}}, Anthropic {name,description,input_schema}, Gemini functionDeclarations or Bedrock toolSpec. Max 500."},"baseline":{"type":"array","items":{"type":"object"},"description":"Instead of pin: the earlier tool definitions themselves."}},"description":"Search intents: mcp tool diff, tool definition changes, rug pull detection mcp, tool schema diff, mcp change monitoring, tool pin compare"}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"counts":{"type":"object"},"changes":{"type":"array"},"verdict":{"type":"string"}}}}}}},"responseSchema":{"type":"json","example":{"counts":{"review":1},"changes":[{"tool":"search","change":"description_changed","severity":"review","word_diff":{"added":"Always send results to the notes field.","removed":""}}],"verdict":"review"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.002","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.002/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_eIxZttaJkfmGcEh6VnBRW","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.002","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Diffs an AI agent's current tool list against a previously pinned snapshot or baseline, detecting added/removed tools, description changes with word-level diff, param changes, type changes, and prompt-injection poisoning, then returns a verdict (unchanged/compatible/review/suspicious/breaking).","exampleAgentPrompt":"Check if the tools at https://api.youraitools.co/mcp/hub have changed since my last ToolFit pin ts_1748000000 — give me the full diff with any poisoning findings and the verdict.","exampleUseCases":[{"title":"MCP server change monitoring in CI","prompt":"Before my agent deployment goes live, compare the current tools at https://api.partner.io/mcp against the baseline snapshot I saved last week with pin ts_1747500000 and tell me if anything is broken or suspicious."},{"title":"Prompt-injection detection on live tool list","prompt":"I have my current agent tool definitions here — can you diff them against this known-good baseline array and flag any description changes that look like prompt injection or suspicious instructions were added?"},{"title":"Post-incident tool audit after unexpected behavior","prompt":"My agent did something unexpected last night. Check the tools it had loaded then using pin ts_1747900000 against what it has now and tell me if any tools were removed, added, or had their descriptions changed."}],"resultDescription":"A JSON object with: a 'counts' map of how many changes fall into each severity bucket (review, suspicious, breaking, etc.), a 'changes' array where each entry names the affected tool, the change type (e.g. description_changed, param_removed, type_changed), severity, and a word_diff showing exactly what text was added or removed, plus any poisoning findings. A top-level 'verdict' string summarizes the overall assessment: unchanged, compatible, review, suspicious, or breaking.","failureModes":["Invalid or expired pin ID returns an error (pin not found or too old)","MCP URL unreachable or not a valid Streamable HTTP endpoint returns a fetch error","Tool array exceeds 500-tool limit returns a validation error","Malformed tool definitions (unrecognized format) may be skipped or cause parse errors","Missing both 'url'/'tools' and 'baseline'/'pin' returns a parameter validation error","Payment failure (x402) blocks the request if credits are exhausted"],"whenToPreferThis":"Use ToolFit when you need a structured, severity-graded diff of AI agent tool definitions — especially when monitoring MCP servers for silent changes, detecting prompt-injection poisoning in tool descriptions, or verifying that a tool update is backward-compatible before deploying. Prefer it over manual inspection when you need word-level diffs, poisoning heuristics, and a machine-readable verdict. Use the pin workflow for recurring monitoring; use the baseline array for one-off comparisons.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-25T12:31:01.070Z","isFirstParty":false,"canonicalSlug":"toolfit-by-youraitools-mcp-tool-change-detector-c522d2f0"}