This Google Calendar MCP server has significant definition quality gaps. All 4 tools have schema definitions visible in the provided specification, with proper type declarations and parameter descriptions. However, the implementation is incomplete: mcp_server.py contains only mock responses ('This is a mock response - configure Google API credentials to use real functionality'), meaning no actual Google Calendar API integration is present. Tool descriptions are minimal (10-50 chars) and lack LLM-optimized guidance on when to use each tool or what side effects occur. Parameter descriptions exist but are generic. No error handling guidance, no output schema documentation, no pagination support for freebusy_query which returns arrays. Tool naming is acceptable (verb_noun pattern: create_event, update_event, delete_event, freebusy_query), but freebusy_query breaks the pattern, should be 'query_freebusy'. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) despite clear risk differentiation (READ_ONLY, WRITE, DESTRUCTIVE). The server initializes with protocolVersion '2025-06-18' which is older than the current spec (2026-07-28). Overall, this reads as an early-stage skeleton with placeholders rather than a production-ready tool suite.
All tool descriptions are critically short (26 - 47 characters) and lack LLM-optimization guidance. Descriptions should be 50 - 200 chars, explain WHEN to use each tool, and highlight differences from similar tools.
No output schema documentation for any tool. LLMs cannot plan downstream calls (e.g., which field contains the event_id for later updates?) without knowing the response structure. All tools should document their return type and key fields.
No tool annotations (destructiveHint, readOnlyHint, idempotentHint) despite clear risk levels declared (READ_ONLY, WRITE, DESTRUCTIVE in metadata). delete_event should have destructiveHint. freebusy_query should have readOnlyHint. update_event and create_event should declare idempotency if supported.
create_eventupdate_eventdelete_event
Recommendations
Expand each tool description to 80 - 150 characters. Format: 'ACTION: [what it does]. WHEN: [when to call instead of similar tools]. RETURNS: [key fields the LLM will need for chaining]. SIDE EFFECTS: [if any].' Example: 'create_event: Creates a calendar event. When: use to add new meetings or reminders. Returns: event_id, event_link (for sharing). Side effects: sends invites to attendees if sendUpdates is not set to none.'
Add output schema documentation for each tool. Either inline in the description or as a separate outputSchema field in the tool definition. Example for create_event: 'Returns {event_id (string), created (ISO 8601), status (confirmed|tentative), attendees_invited (int), event_link (string)}'.
Add tool annotations: delete_event.destructiveHint=true; freebusy_query.readOnlyHint=true; create_event.idempotentHint=(depends on implementation, if request_id deduping is used, set true); update_event.idempotentHint=(same).
Rename freebusy_query to query_freebusy to match verb_noun convention.
For attendees parameter (create_event, update_event, delete_event), clarify format: 'List of attendee email addresses. Examples: ["alice@example.com", "bob@example.com"]. Optionally include display names: ["Alice Smith <alice@example.com>"].'
Document parameter constraints in descriptions. Examples: 'calendarId: the unique identifier of the target calendar (e.g., primary, or user@domain.com). summary: event title, 1 - 500 characters. startTime/endTime: ISO 8601 format (e.g., 2024-12-25T14:30:00Z). timezone: IANA timezone name (e.g., America/New_York). If omitted, defaults to the calendar's timezone.'
Spec posture evidence
Inferred effective spec: <=2025-11-25.
Relies on Logging (deprecated) - log to stderr or use OpenTelemetry
freebusy_query violates verb_noun naming convention. Name should be 'query_freebusy' or 'get_freebusy' (verb_noun format). Current name 'freebusy_query' reads as noun_verb.
No error handling guidance or recovery patterns. If create_event fails due to timezone mismatch or attendee email validation, the response should suggest what to try next (e.g., 'Invalid timezone. Call get_timezones() to see supported values.'). Currently, errors will be mock responses.
Implementation is non-functional, mcp_server.py returns mock responses for all tool calls with placeholder text ('This is a mock response - configure Google API credentials...'). Actual Google Calendar API integration is absent; adapters/calendar.py and router/queue.py are not provided or are stubs.
Parameter relationships undocumented. For create_event and update_event, what happens if only startTime is provided without endTime? Can endTime be before startTime? Are attendees required? Are any fields mutable post-creation?
freebusy_query lacks pagination support. Querying many calendars or long time windows could return thousands of busy blocks. No limit, offset, or cursor parameters provided. Response could explode token usage.
freebusy_query
Add error handling guidance. Example for create_event: 'Common errors: (1) Invalid timezone → suggest calling a hypothetical get_timezones() tool; (2) attendee email format invalid → return the invalid email and suggest correction; (3) startTime after endTime → return clearly what was received vs. constraints.'
Implement actual Google Calendar API calls in adapters/calendar.py and router/queue.py. Replace all mock responses with real calendar operations. Test against live Google Calendar API.
For freebusy_query, add pagination: 'limit (int, default 100, max 1000): max time blocks to return per calendar. next_cursor (string, optional): pagination token for large result sets.'
Add parameter-relationship documentation: 'For create_event/update_event, if only startTime is provided, endTime defaults to startTime + 1 hour. startTime must be before endTime. All attendees must have valid email format. If an attendee is already invited, the operation does not error, it updates their status.'
Consider adding an idempotency key or request_id parameter to create_event and update_event if not already supported by the Google Calendar API. This prevents duplicate events if the client retries on network failure.