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

Annotations already cover read-only, idempotent, open-world, non-destructive behavior, so the bar is lower. The description still adds real value with 'Never returns RSVP or attendee lists', a negative scope disclosure about output the agent cannot get from any structured field.

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

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

Two short sentences, front-loaded with what is returned and how it is keyed, then the two behavioral facts that matter (default scope, excluded data). No filler.

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

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

Three params with full schema coverage, rich annotations, and no output schema, so the description needn't document return shape. It covers default behavior and data exclusions; only the boundary against sibling event tools is left implicit.

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

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

Schema description coverage is 100%, including range and default for `limit`, an example for `urlname`, and the semantics of `include_past`. The description repeats the include_past behavior but adds nothing new about parameters, so baseline 3 applies.

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

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

States a specific verb and resource ('List a Meetup group's events') and pins the access key ('by the group's urlname'), which separates it from keyword-style siblings like meetup_search_events. It never names a sibling explicitly, so differentiation is inferred rather than stated.

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

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

The description explains the default mode (upcoming) and the switch for past events via `include_past`, which is genuine usage guidance. It gives no guidance on when to pick this over meetup_search_events or meetup_event, so the caller must infer the boundary.

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