factreason

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factreason_api_schema

Read-onlyIdempotent

Retrieve exact API request and response schemas for third-party services. Pass a service or query to locate matching endpoints or closest alternatives.

Instructions

Search exact request and response schemas for third-party API endpoints. Pass service alone to list its indexed endpoints, add query to narrow by path or operation, or use query alone across services; returns matches or nearest services. Uses metered access and does not modify source data. Prefer factreason_integration_brief for one callable request.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`query`	No	Optional endpoint path or operation, e.g. "payment_intents"
`service`	No	Optional service filter, e.g. "Stripe"

Output Schema

TableJSON Schema

Name	Required	Description	Default
`hint`	No
`found`	No
`message`	No
`results`	No
`totalMatched`	No
`nearestServices`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedv2.0.2Aug 14, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / query / description

Previous value: -"Endpoint path or operation, e.g. \"payment_intents\", \"chat/completions\""New value: +"Optional endpoint path or operation, e.g. \"payment_intents\""

addedInput schema / properties / query / minLength
```
Added value: +1
```

changedInput schema / properties / service / description

Previous value: -"Service name, e.g. \"Stripe\""New value: +"Optional service filter, e.g. \"Stripe\""

addedInput schema / properties / service / minLength
```
Added value: +1
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "found": {
+      "type": "boolean"
+    },
+    "hint": {
+      "type": "string"
+    },
+    "message": {
+      "type": "string"
+    },
+    "nearestServices": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "results": {
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "totalMatched": {
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

First observedv2.0.1Aug 14, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds two useful behaviors beyond that: 'Uses metered access' (cost/rate-limit implication) and 'returns matches or nearest services' (fuzzy fallback). This extra context helps an agent anticipate side effects and output behavior without contradicting the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, each with a distinct job: purpose, usage modes, and behavior plus alternative. No fluff, no repetition of schema field names. The most important information is front-loaded, and the alternative recommendation is strategically placed at the end.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only search tool with a rich output schema and full annotations, the description covers all necessary aspects: what it searches, how to invoke it in three modes, the metered-access caveat, and a pointer to an adjacent tool. The existence of an output schema means return-value details need not be spelled out, and the description does not attempt to over-explain.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema already documents each parameter individually, and coverage is 100%. The description goes further by explaining parameter combinations: 'Pass service alone to list its indexed endpoints, add query to narrow by path or operation, or use query alone across services.' This clarifies how the two optional parameters interact, which is not evident from the schema alone.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb-resource pairing: 'Search exact request and response schemas for third-party API endpoints.' It immediately clarifies the tool's scope (schemas, not code or documentation) and distinguishes it from the sibling tool factreason_integration_brief by explicitly recommending that tool for 'one callable request.' The usage modes (service alone, query narrows, query alone) further sharpen the purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives concrete usage scenarios: 'Pass service alone to list its indexed endpoints, add query to narrow by path or operation, or use query alone across services.' It also names an alternative tool ('Prefer factreason_integration_brief for one callable request'), providing a clear when-to-use-this-over-that rule. However, it does not mention other sibling tools like factreason_discover_api or factreason_api_breaking_changes, so coverage of alternatives is not exhaustive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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