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

Annotations already establish the read-only, idempotent, closed-world profile, so the bar is lower. The description adds genuinely useful context beyond that: email addresses are never returned (privacy boundary) and counts keep changing for days after a send (eventual consistency), which affects how an agent should interpret and re-query results.

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?

Front-loaded with the core answer, then a sentence expanding the return contents, then a caveat about freshness. Mostly tight, though the opening phrase 'the subscribers it won and lost' is re-specified in the next sentence, costing a little redundancy.

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 no output schema, the description carries the burden of explaining return values and does so thoroughly, including privacy scope and freshness caveats. What remains unclear is only how this relates to sibling stats tools, a minor gap for a single-parameter read.

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?

Only one parameter and schema description coverage is 100%; the schema already explains post_id comes from list_posts. The description adds no format or sourcing detail beyond that, so the baseline of 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 resource and enumerates exactly what is returned: likes, comments with names/handles, and signups/subscriptions/unsubscribes. 'The Engagement and Growth parts of a post's stats' implicitly carves out scope against siblings like get_post_stats and get_post_traffic, though no sibling is named directly.

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?

Usage is implied by the division of a post's stats into parts, which suggests this tool covers engagement/growth while others cover the rest. However, there is no explicit when-to-use or when-not-to-use statement naming an alternative tool.

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