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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) }] })
Behavior2/5

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

No annotations are provided, so the description carries full burden for behavioral disclosure. While 'List all labels' implies a read-only operation, the description doesn't address important behavioral aspects like whether this returns all labels at once or uses pagination, what format the labels are returned in, or any authentication requirements. For a tool with zero annotation coverage, this represents significant gaps.

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, efficient sentence that communicates the core purpose without any wasted words. It's appropriately sized for a simple list operation and front-loads the essential information, making it easy for an agent to parse quickly.

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?

For a simple list operation with no parameters and no output schema, the description provides the minimum viable information about what the tool does. However, without annotations or output schema, the agent lacks important context about the return format, pagination behavior, and authentication requirements that would be helpful for proper tool invocation.

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?

With 0 parameters and 100% schema description coverage, the baseline score would be 4 even with no parameter information in the description. The description correctly aligns with the empty parameter schema by not mentioning any parameters, which is appropriate for this simple list operation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('List all labels') and target resource ('in the user's mailbox'), providing a specific verb+resource combination. However, it doesn't distinguish this tool from its sibling 'get_label' (which presumably retrieves a single label), missing explicit differentiation that would warrant a perfect score.

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 provides no guidance on when to use this tool versus alternatives. With sibling tools like 'get_label' (for single label retrieval) and 'create_label' (for label creation), the agent receives no explicit or implied direction about appropriate contexts, exclusions, or prerequisites for using this list operation.

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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