Gmail MCP Server

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list_delegates

View and manage delegated access to a Gmail account by listing authorized users who can send emails or manage messages on your behalf.

Instructions

Lists the delegates for the specified account

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Implementation Reference

src/index.ts:987-996 (handler)

The handler function for the 'list_delegates' tool. It uses handleTool to authenticate and calls the Gmail API gmail.users.settings.delegates.list to retrieve the list of delegates for the user's account, then formats the response.

server.tool("list_delegates",
  "Lists the delegates for the specified account",
  {},
  async () => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.settings.delegates.list({ userId: 'me' })
      return formatResponse(data)
    })
  }
)

src/index.ts:987-996 (registration)

Registration of the 'list_delegates' tool on the MCP server using server.tool, including description, empty input schema, and inline handler.

server.tool("list_delegates",
  "Lists the delegates for the specified account",
  {},
  async () => {
    return handleTool(config, async (gmail: gmail_v1.Gmail) => {
      const { data } = await gmail.users.settings.delegates.list({ userId: 'me' })
      return formatResponse(data)
    })
  }
)

src/index.ts:989-989 (schema)
Input schema for list_delegates tool: empty object, indicating no parameters required.
```
{},
```

src/index.ts:50-66 (helper)

Shared helper function handleTool used by list_delegates (and other tools) to handle OAuth2 authentication, client creation, and execute the Gmail API call.

const handleTool = async (queryConfig: Record<string, any> | undefined, apiCall: (gmail: gmail_v1.Gmail) => Promise<any>) => {
  try {
    const oauth2Client = queryConfig ? createOAuth2Client(queryConfig) : defaultOAuth2Client
    if (!oauth2Client) throw new Error('OAuth2 client could not be created, please check your credentials')

    const credentialsAreValid = await validateCredentials(oauth2Client)
    if (!credentialsAreValid) throw new Error('OAuth2 credentials are invalid, please re-authenticate')

    const gmailClient = queryConfig ? google.gmail({ version: 'v1', auth: oauth2Client }) : defaultGmailClient
    if (!gmailClient) throw new Error('Gmail client could not be created, please check your credentials')

    const result = await apiCall(gmailClient)
    return result
  } catch (error: any) {
    return `Tool execution failed: ${error.message}`
  }
}

src/index.ts:48-49 (helper)
Helper function to format the API response into MCP content format, used by list_delegates.
```
const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })
```

Schema Changelog

Changes observed during successful MCP inspections.

First observedDec 8, 2025

TDQS

A3.9/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It states a read operation (list), which is transparent, but it does not disclose any behavioral traits such as permissions required, potential side effects, or return format.

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 a single concise sentence with no wasted words. It is front-loaded with the key information.

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

Completeness3/5

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

Given no output schema and zero parameters, the description is minimal. It does not mention what the list contains, pagination, or ordering. For a simple list tool, this is adequate but could provide more detail about the output.

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 input schema has no parameters, so there is nothing to document. With 100% schema coverage and zero parameters, the description does not need to add parameter meaning beyond the schema; the baseline of 4 applies.

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 it lists delegates for the specified account, using a specific verb ('Lists') and resource ('delegates'). It distinguishes from siblings like add_delegate (add), get_delegate (single), and remove_delegate (delete).

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?

The description does not explicitly state when to use this tool vs alternatives like get_delegate. It implies a listing operation, but no exclusions or context for when to choose listing over retrieving a single delegate are given.

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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