Primary Sources

mcp_registry_search

Read-onlyIdempotent

Search the official MCP Registry for installable MCP servers (free, no key). Returns server names, titles, descriptions, versions and repository URLs. Use to discover MCP servers by capability.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No	Max servers, default 20
`query`	No	Search text, e.g. postgres

Output Schema

TableJSON Schema

Name	Required	Description
`data`	Yes	Source payload; fields vary per tool
`source`	Yes	Human-readable upstream source name
`retrievedAt`	Yes	ISO-8601 timestamp of retrieval

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 3, 2026

addedInput schema / properties / limit / description
```
Added value: +"Max servers, default 20"
```
addedInput schema / properties / query / description
```
Added value: +"Search text, e.g. postgres"
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "data": {
+      "description": "Source payload; fields vary per tool",
+      "type": "object"
+    },
+    "retrievedAt": {
+      "description": "ISO-8601 timestamp of retrieval",
+      "type": "string"
+    },
+    "source": {
+      "description": "Human-readable upstream source name",
+      "type": "string"
+    }
+  },
+  "required": [
+    "source",
+    "retrievedAt",
+    "data"
+  ],
+  "type": "object"
+}

First observedOct 3, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely non-structured context: the registry is 'free, no key' (no auth setup required) and it enumerates what the results contain. It does not discuss pagination or result limits beyond the schema default.

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 tight sentences: what it searches, what it returns, when to use it. Front-loaded with the action and resource, no filler, nothing repeated.

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?

The tool is simple (2 optional params), an output schema exists so return values need not be explained, and annotations cover safety. The description still covers source, cost/auth, and return shape – more than sufficient for correct invocation.

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

Parameters3/5

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

Schema description coverage is 100% (both 'limit' and 'query' are documented in-schema, with an example). The description adds nothing about parameter behavior, so the baseline of 3 applies – the schema does all the parameter work.

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 specific verb (Search) and a specific resource (the official MCP Registry for installable MCP servers), and names the scope constraint (installable servers). It is immediately distinguishable from every sibling, all of which query unrelated data sources.

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?

Explicitly states the use case: 'Use to discover MCP servers by capability.' That gives a clear trigger condition. It stops short of naming when not to use it or pointing at an alternative, but no sibling competes for this job, so the omission is minor.

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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