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taylorwilsdon

Google Workspace MCP Server - Control Gmail, Calendar, Docs, Sheets, Slides, Chat, Forms & Drive

start_google_auth

Initiates Google OAuth 2.0 authentication to grant access to specific Google services like Gmail, Drive, or Calendar. Generates an authorization URL for users to complete sign-in, enabling secure credential establishment for the current session.

Instructions

Initiates the Google OAuth 2.0 authentication flow for the specified user email and service.
This is the primary method to establish credentials when no valid session exists or when targeting a specific account for a particular service.
It generates an authorization URL that the LLM must present to the user.
The authentication attempt is linked to the current MCP session via `mcp_session_id`.

LLM Guidance:
- Use this tool when you need to authenticate a user for a specific Google service (e.g., "Google Calendar", "Google Docs", "Gmail", "Google Drive")
  and don't have existing valid credentials for the session or specified email.
- You MUST provide the `user_google_email` and the `service_name`. If you don't know the email, ask the user first.
- Valid `service_name` values typically include "Google Calendar", "Google Docs", "Gmail", "Google Drive".
- After calling this tool, present the returned authorization URL clearly to the user and instruct them to:
    1. Click the link and complete the sign-in/consent process in their browser.
    2. Note the authenticated email displayed on the success page.
    3. Provide that email back to you (the LLM).
    4. Retry their original request, including the confirmed `user_google_email`.

Args:
    user_google_email (str): The user's full Google email address (e.g., 'example@gmail.com'). This is REQUIRED.
    service_name (str): The name of the Google service for which authentication is being requested (e.g., "Google Calendar", "Google Docs"). This is REQUIRED.
    mcp_session_id (Optional[str]): The active MCP session ID (automatically injected by FastMCP from the Mcp-Session-Id header). Links the OAuth flow state to the session.

Returns:
    str: A detailed message for the LLM with the authorization URL and instructions to guide the user through the authentication process.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
mcp_session_idNo
service_nameYes
user_google_emailYes
Behavior4/5

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

With no annotations provided, the description carries full behavioral disclosure burden. It effectively describes the tool's behavior: generates authorization URLs, links authentication to MCP sessions, requires user interaction, and provides detailed post-call instructions. It doesn't mention rate limits or error conditions, but covers the core authentication flow comprehensively.

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?

The description is well-structured with clear sections (purpose, LLM Guidance, Args, Returns) but could be more concise. The 'LLM Guidance' section contains some redundancy (e.g., repeating service examples). However, every sentence serves a purpose in guiding the agent through the authentication workflow.

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?

For an authentication tool with 3 parameters, no annotations, and no output schema, the description provides exceptional completeness. It covers the authentication flow, parameter requirements, valid values, session linking, and detailed post-call instructions. The agent has all necessary context to use this tool correctly without additional documentation.

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

Parameters5/5

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

Despite 0% schema description coverage, the description provides extensive parameter semantics in the 'Args' section. It explains each parameter's purpose, provides examples, clarifies requirements ('REQUIRED'), and offers guidance on valid values for service_name. This fully compensates for the schema's lack of descriptions.

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 the specific action ('Initiates the Google OAuth 2.0 authentication flow') and target resources ('for the specified user email and service'). It distinguishes itself from sibling tools by focusing exclusively on authentication initiation rather than document/event/content operations.

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

Usage Guidelines5/5

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

The 'LLM Guidance' section provides explicit when-to-use instructions ('when you need to authenticate... and don't have existing valid credentials'), clear prerequisites ('MUST provide user_google_email and service_name'), and specific alternatives ('If you don't know the email, ask the user first'). It also outlines the complete workflow after tool invocation.

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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