Glean Connector MCP Server

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update_schema

Write field definitions to the Glean schema file. Use after infer_schema to save the schema or to manually update fields, with optional merge to combine with existing schema.

Instructions

Write field definitions to .glean/schema.json. Call this after infer_schema to save the agreed schema, or to make manual edits. Set merge: true to merge incoming fields with the existing schema (fields with the same name are replaced; new names are appended) instead of replacing the entire field list.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "fields": "<fields>"
    },
    "name": "update_schema"
  }
}

Input Schema

Name	Required	Description	Default
`merge`	No	If true, merge incoming fields with the existing schema (fields with the same name are replaced; new names are appended). If false (default), the entire field list is replaced.
`fields`	Yes	Field definitions to write to .glean/schema.json

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.6.0Jul 28, 2026

TDQS

A4.4/5.0

Behavior4/5

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

No annotations are provided, so the description carries full burden. It details the write action, file path, and merge behavior (replace vs append). It lacks info on side effects like file creation or permissions, but the given detail is good.

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 concise sentences: first states action and file, second gives usage context, third explains merge parameter. No redundancy or fluff.

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?

For a 2-parameter tool with no output schema, the description covers the action, usage context, and parameter behavior. It lacks error handling or side effects, but is fairly complete given low complexity.

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% (baseline 3). The description adds value by explaining merge: true behavior (replace same name, append new) and the context of using after infer_schema, surpassing schema descriptions.

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 clearly states the tool writes field definitions to .glean/schema.json (specific verb+resource). It distinguishes itself from siblings like infer_schema by stating it is called after infer_schema to save the agreed schema, and from get_schema which reads.

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 explicitly says when to use: after infer_schema to save or for manual edits. It explains the merge behavior and default. However, it does not explicitly state when not to use or provide alternative tools beyond the implicit sequence.

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