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list_labels

Retrieve all email labels from your Gmail account to organize and categorize messages for better email management.

Instructions

List all labels in the user's mailbox

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • Registration, schema (empty input), and handler for the 'list_labels' tool. The handler authenticates via handleTool, calls the Gmail API gmail.users.labels.list to fetch all labels for the user, and returns a formatted JSON response.
    server.tool("list_labels",
      "List all labels in the user's mailbox",
      {},
      async () => {
        return handleTool(config, async (gmail: gmail_v1.Gmail) => {
          const { data } = await gmail.users.labels.list({ userId: 'me' })
          return formatResponse(data)
        })
      }
    )
  • Helper function used by list_labels (and other tools) to handle OAuth2 authentication, validate credentials, create Gmail client, execute the API call, and handle errors.
    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}`
      }
    }
  • Helper function to format the API response into MCP content structure with JSON stringified text.
    const formatResponse = (response: any) => ({ content: [{ type: "text", text: JSON.stringify(response) }] })

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

B3.4/5.0
Behavior2/5

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

With no annotations, the description carries the full burden. It indicates a safe read operation but lacks details about potential rate limits, ordering, or pagination. The description is minimal and does not disclose any behavioral traits beyond the basic function.

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 extraneous words. It is front-loaded and every word contributes to the purpose.

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

Completeness2/5

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

Given the simplicity of the tool (no params, no output schema), the description is complete in stating its core purpose. However, it lacks details about the return format or any limitations, which would be helpful for an agent. The description is adequate but not fully informative.

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 has zero parameters, and the schema coverage is trivially 100%. Per guidelines, a baseline of 4 is assigned since no parameter information is needed.

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 explicitly states the verb 'list', the resource 'labels', and the scope 'user's mailbox'. This clearly distinguishes it from sibling tools like create_label, delete_label, and get_label.

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

Usage Guidelines2/5

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

The description does not provide any guidance on when to use this tool versus alternatives, nor does it mention when not to use it or prerequisites. It simply states what it does, leaving the agent to infer the context.

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