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

Annotations already declare readOnlyHint=true, so the description's job is lighter. It adds that the output includes counts and percentage change, but does not disclose potential rate limits, auth requirements, or behavior when no events exist. Adequate but not above baseline.

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 sentences, directly to the point. Every sentence adds value: the first explains what the tool does, the second suggests use case and exposes the API endpoint. No wasted words.

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?

With 2 optional parameters, no output schema, and readOnlyHint annotation, the description covers purpose and usage adequately. It might benefit from a brief note on return format, but it is complete enough for a simple discovery tool.

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% – both 'type' and 'limit' have clear descriptions in the input schema. The tool description adds no extra parameter information beyond what is already structured, so a baseline of 3 is appropriate.

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?

The description states 'List today's top events with counts and % change vs yesterday' – a specific verb and resource. Suggests its role as a first call for discovery, distinguishing it from more complex query tools like mixpanel_segmentation or mixpanel_jql.

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 phrase 'Good first call to discover what events a project tracks' provides clear usage context. However, it does not explicitly exclude alternatives or mention when not to use it, which prevents a perfect score.

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