Schema quality: missing property descriptions across official MCP servers

[KryptosAI]

Summary

While running automated quality checks against the official MCP reference servers, I found that most servers are missing description fields on their tool input schema properties. This matters because LLMs use these descriptions to understand how to call tools correctly — without them, the model has to guess what each parameter means from the name alone.

Findings

Tested with MCP Observatory v0.13.0 on 2026-03-22.

server-filesystem (11 tools, 18 missing descriptions)

Every tool property across all 11 tools lacks a description:

• read_file: path missing description
• write_file: path, content missing descriptions
• edit_file: path, edits missing descriptions
• create_directory: path missing description
• list_directory: path missing description
• directory_tree: path, excludePatterns missing descriptions
• move_file: source, destination missing descriptions
• search_files: path, pattern, excludePatterns missing descriptions
• get_file_info: path missing description

server-everything (13 tools, 5 missing descriptions + 4 missing required)

• get-resource-reference: resourceType missing description
• 4 tools missing required array: get-resource-links, get-resource-reference, gzip-file-as-resource, trigger-long-running-operation
• Resource README.md.gz missing description

server-memory (6 tools, 4 missing descriptions)

• create_entities: entities missing description
• create_relations: relations missing description
• add_observations: observations missing description
• delete_observations: deletions missing description

Why this matters

The MCP spec recommends tool input schemas follow JSON Schema with descriptions. When an LLM sees:

{ "type": "string" }

vs:

{ "type": "string", "description": "Absolute or relative path to the file to read" }

The second version produces significantly better tool-use accuracy. Since these are the reference implementations that other server authors look at, setting a good example here would improve schema quality across the ecosystem.

Suggested fix

Add description fields to all tool input schema properties. Example for read_file:

inputSchema: {
  type: "object",
  properties: {
    path: {
      type: "string",
      description: "Absolute or relative path to the file to read"
    }
  },
  required: ["path"]
}

Reproduction

npx @kryptosai/mcp-observatory score npx -y @modelcontextprotocol/server-filesystem /tmp
npx @kryptosai/mcp-observatory score npx -y @modelcontextprotocol/server-everything
npx @kryptosai/mcp-observatory score npx -y @modelcontextprotocol/server-memory

[khalidsaidi]

A2ABench has an accepted answer for this imported thread.

• Thread: https://a2abench-api.web.app/q/cmn1ngym4007rxzty2esf43c0
• Accepted at: 2026-03-24T20:32:25.823Z
• Accepted answer agent: ai village
• Answer preview: "Based on our strict principles of idempotent execution, trace-first architecture, and explicit workflow boundaries, this issue regarding 'Schema quality: missing property descriptions across official MCP servers' can be resolved by enforcing stateless handlers and explicit loop c"

[radeshgovind-2005]

Hi, I've submitted PR #3732 which addresses all the points raised in this issue.