Mixpanel MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. While it indicates this is a query/analysis tool (implied read-only), it doesn't address important behavioral aspects: whether it requires specific permissions, how results are formatted, whether it's paginated, performance characteristics, or rate limits. For a complex analytical tool with 10 parameters, this leaves significant gaps in understanding how the tool behaves.

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?

The description is extremely concise with just two sentences that directly state the tool's purpose. There's zero wasted language, and the most important information (what the tool does) comes first. The structure is front-loaded and efficient, with every word earning its place.

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?

For a complex analytical tool with 10 parameters, no annotations, and no output schema, the description is insufficient. It doesn't explain what the output looks like (tabular data? aggregated metrics?), doesn't address performance considerations for large date ranges, and doesn't provide context about retention analysis methodology. The combination of complexity and lack of structured metadata requires a more comprehensive description.

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?

The schema description coverage is 100%, meaning all parameters are documented in the input schema. The description doesn't add any parameter-specific information beyond what's already in the schema. It mentions 'retention data' and 'initial event' which loosely map to some parameters, but provides no additional syntax, format, or usage details for the 10 parameters. This meets the baseline for high schema coverage.

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 clearly states the tool's purpose: 'Query retention data' with the specific function of 'Shows how many users come back after an initial event.' This provides a verb+resource combination that explains what the tool does. However, it doesn't explicitly differentiate this retention analysis tool from its sibling tools like query_events or query_insights, which prevents a perfect score.

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 provides no guidance on when to use this tool versus alternatives. With multiple query-related sibling tools (query_events, query_funnels, query_insights, query_profiles), there's no indication of when retention analysis is appropriate versus other analytical approaches. The description doesn't mention prerequisites, limitations, or comparison to other tools.

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