FactReason

API schema search

factreason_api_schema

Read-onlyIdempotent

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
`query`	No	Optional endpoint path or operation, e.g. "payment_intents"
`apiKey`	No	Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
`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.

Changed1 schema field changedOct 4, 2026

addedInput schema / properties / apiKey

Added value: +{
+  "description": "Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}

Changed6 schema fields changedAug 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 observedAug 14, 2026

TDQS

A4.7/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds value beyond that: 'Uses metered access' (a cost implication not in the annotations) and 'returns matches or nearest services' (a fallback behavior worth knowing). It stops short of describing latency or result ranking, so a 4 rather than 5.

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?

Two sentences, front-loaded with the primary purpose, then the mode semantics and the sibling alternative. No filler and every clause carries information.

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?

With an output schema present, return values need no explanation. Combined with full schema coverage and rich annotations, the description covers purpose, modes, fallback behavior, cost, and the alternative tool — nothing material is missing for correct invocation.

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?

Schema coverage is 100%, so baseline is 3, but the description goes beyond the schema by explaining how parameters combine — service alone, service+query, or query alone — which the schema cannot convey since every property is individually marked optional.

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?

States a precise verb and resource: 'Search exact request and response schemas for third-party API endpoints.' This is distinct from siblings like factreason_discover_api and factreason_component_spec, and it explicitly names factreason_integration_brief as the alternative for a different need.

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

Usage Guidelines5/5

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

Explicitly enumerates the invocation modes: '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 the sibling alternative and the condition ('for one callable request') that selects it.

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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