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set_default_smime_info

Configure the default S/MIME encryption settings for a specific email alias in Gmail to secure outgoing messages.

Instructions

Sets the default S/MIME config for the specified send-as alias

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
sendAsEmailYesThe email address that appears in the 'From:' header
idYesThe immutable ID for the S/MIME config

Implementation Reference

  • Handler for 'set_default_smime_info' tool: authenticates via handleTool and calls Gmail API gmail.users.settings.sendAs.smimeInfo.setDefault to set the default S/MIME config for a send-as alias.
    async (params) => {
      return handleTool(config, async (gmail: gmail_v1.Gmail) => {
        const { data } = await gmail.users.settings.sendAs.smimeInfo.setDefault({ userId: 'me', sendAsEmail: params.sendAsEmail, id: params.id })
        return formatResponse(data)
      })
    }
  • Zod input schema defining parameters: sendAsEmail (string) and id (string).
      sendAsEmail: z.string().describe("The email address that appears in the 'From:' header"),
      id: z.string().describe("The immutable ID for the S/MIME config")
    },
  • src/index.ts:1289-1301 (registration)
    Registers the 'set_default_smime_info' tool on the MCP server with description, schema, and handler.
    server.tool("set_default_smime_info",
      "Sets the default S/MIME config for the specified send-as alias",
      {
        sendAsEmail: z.string().describe("The email address that appears in the 'From:' header"),
        id: z.string().describe("The immutable ID for the S/MIME config")
      },
      async (params) => {
        return handleTool(config, async (gmail: gmail_v1.Gmail) => {
          const { data } = await gmail.users.settings.sendAs.smimeInfo.setDefault({ userId: 'me', sendAsEmail: params.sendAsEmail, id: params.id })
          return formatResponse(data)
        })
      }
    )
  • Shared helper function used by all Gmail tools, including set_default_smime_info, to handle OAuth2 authentication, create Gmail client, execute API calls, and format 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) {
        // Check for specific authentication errors
        if (
          error.message?.includes("invalid_grant") ||
          error.message?.includes("refresh_token") ||
          error.message?.includes("invalid_client") ||
          error.message?.includes("unauthorized_client") ||
          error.code === 401 ||
          error.code === 403
        ) {
          return formatResponse({
            error: `Authentication failed: ${error.message}. Please re-authenticate by running: npx @shinzolabs/gmail-mcp auth`,
          });
        }
    
        return formatResponse({ error: `Tool execution failed: ${error.message}` });
      }
    }

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

C2.9/5.0
Behavior2/5

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

With no annotations, the description carries full burden for behavioral traits. It fails to disclose whether the operation is idempotent, if it overrides an existing default, what happens if the config doesn't exist, or any required permissions.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single sentence that is front-loaded and efficient. However, it could incorporate additional context without becoming overly verbose, such as specifying that the config must already exist.

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?

The tool is simple with two required parameters and no output schema. The description covers the core purpose but lacks behavioral details and differentiation from siblings. It is adequate but not fully complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, defining sendAsEmail and id. The description adds no further meaning beyond the schema, which is sufficient for a baseline 3.

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 (sets) and the resource (default S/MIME config) with context (for a send-as alias). It differentiates from siblings like insert_smime_info and delete_smime_info, but does not explicitly contrast them.

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?

No guidance on when to use this tool versus alternatives like insert_smime_info or list_smime_info. The description implies setting a default, but does not specify prerequisites or scenarios where this tool is preferred.

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