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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the description doesn't need to repeat those. It adds value by stating the return content (event names, timestamps, properties), which is not covered by annotations. However, it does not disclose any rate limits, pagination behavior, or authentication nuances beyond the schema's _apiKey description.

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 two sentences: a clear purpose statement followed by a concrete usage example. It is front-loaded with the action and resource, and the example illustrates parameter usage. Every word earns its place, with no fluff or repetition.

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?

Given that an output schema exists, the description needn't detail return structure. The tool has only 3 parameters, all documented in the schema, and the description provides an example call. It covers the essentials for correct invocation. Minor gaps like time-range specification are not critical for basic usage.

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%, so all three parameters (limit, _apiKey, project_id) have descriptions in the schema. The description's example mirrors the schema without adding new semantics or clarifying constraints beyond what the schema already specifies. It meets the baseline but adds no extra insight.

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 a specific verb and resource: 'Fetch recent events from a PostHog project.' It also lists the returned fields (names, timestamps, properties) and provides a concrete example call. This clearly distinguishes it from siblings like get_persons or get_insights, which target different data types, even without naming them.

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 offers no guidance on when to use this tool versus alternatives. It doesn't mention that for insights or persons one should use other tools, nor does it state any conditions or prerequisites beyond the required parameters. The example helps with invocation but not with selection among siblings.

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