slack-mcp

resolve_user_id

Read-only

Find a Slack user's ID by entering their name, @handle, or email. Returns up to 5 matches with user details for accurate identification.

Instructions

Resolve a Slack user ID from a name, @handle, or email address.

Searches the full workspace member list (cached for 24h). Returns up to 5 matches sorted by relevance: exact handle > exact email > case-insensitive name > partial substring match. Each result contains id, handle, real_name, display_name, and email.

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": {
      "query": "<query>"
    },
    "name": "resolve_user_id"
  }
}

Input Schema

Name	Required	Description	Default
`query`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 30, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Even with readOnlyHint and destructiveHint annotations already present, the description adds substantial behavioral detail: 24-hour cache, full workspace member list, search relevance ordering, and result fields. This gives an agent accurate expectations beyond what annotations provide.

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?

The description is four sentences with no filler: purpose, scope/cache, matching semantics, and result shape. Every sentence contributes meaningful information and the most important purpose is front-loaded.

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?

Given the single parameter, presence of an output schema, and helpful annotations, the description covers everything needed to call the tool correctly: accepted input, scope, relevance order, result count, and returned fields. No critical operational detail is missing.

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 0%, so the description must carry the parameter meaning, and it does by explaining that query accepts a name, @handle, or email address. This directly compensates for the sparse schema, though it could be slightly more specific about exact matching behavior for handles or emails.

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 opens with a specific verb and resource: 'Resolve a Slack user ID from a name, @handle, or email address.' It clearly distinguishes this tool from channel-related siblings and similar lookup tools with the mention of full workspace member search and match format.

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 provides clear context on when to use it: whenever a user ID needs to be resolved from identifying information. It states the input formats and search scope, though it does not explicitly name alternatives or give when-not-to-use guidance, so it stops short of a 5.

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