YC GraphQL MCP

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yc_describe_schema

Read-onlyIdempotent

Reads YC GraphQL query, mutation, and subscription root type names via introspection, helping clients discover available operations before building or running requests.

Instructions

Read YC query, mutation, and subscription root type names using introspection.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "yc_describe_schema"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`ok`	Yes
`data`	No
`error`	No
`untrustedContent`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.1.0Nov 12, 2026

TDQS

A3.7/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint, so the safety profile is fully covered. The description adds that the read is performed via introspection and enumerates the three root types it covers, but nothing about cost, latency, or whether the schema snapshot is live versus cached — a relevant trait for an openWorld introspection call.

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?

A single front-loaded sentence with no filler, hedging, or repetition. Every word (YC, the three root types, introspection) carries information.

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

Completeness4/5

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

Complexity is minimal: no parameters and an output schema exists, so return values need no explanation in prose. The only meaningful gap for a 16-tool server is the absence of any sequencing hint telling the agent this is the discovery entry point relative to yc_introspect_schema and yc_describe_type.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The sentence does not misleadingly imply any inputs exist.

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

Purpose4/5

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

States a specific verb ("Read") and a precisely scoped resource ("query, mutation, and subscription root type names"), which is narrower than the sibling yc_introspect_schema and distinct from yc_describe_type. An agent can tell what it returns without opening the output schema, though the description never names those siblings to reinforce the contrast.

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

Usage Guidelines3/5

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

Usage is only implied: reading root type names is naturally a discovery step before yc_query or yc_commit_mutation, but the description never says "call this first" or states when to prefer yc_introspect_schema or yc_describe_type instead. No exclusions or prerequisites are given.

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