Summarise performance across recent posts

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it explains the statistical skew (one viral post drags the mean) and implicitly indicates the tool computes aggregate analytics rather than raw data. This extra guidance raises it above baseline, but it doesn't describe return format or error behavior, so a 4 is appropriate.

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 with zero waste. The first sentence front-loads the aggregate metrics and scope ('recent posts'), and the second gives both an alternative and a statistical caveat. Every word earns its place, and the most important usage guidance appears early.

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?

The tool has no output schema, but the description enumerates the exact metrics it returns, effectively serving as the output spec. It also covers usage guidance and statistical interpretation. Given annotations already handle the safety profile, and the description is sufficient for an agent to know what it will get, only minor gaps remain (e.g., explicit return structure or default account behavior, which is in the schema). This is reasonably complete.

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 `scan` and `account` have complete descriptions. The description mentions 'recent posts' which loosely relates to `scan`, but it adds no additional parameter syntax or format details beyond what the schema provides. With full schema coverage, the baseline of 3 is correct; the description does not enhance parameter understanding.

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 aggregates stats over recent posts and enumerates the specific metrics (total/mean views, median/90th percentile, engagement rate, posting interval). It explicitly contrasts with listing videos, distinguishing it from sibling tools like list_videos. This is a specific verb+resource with clear scope.

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 explicitly says 'Reach for this instead of listing videos and adding them up,' naming the alternative and the condition that selects this tool. It also provides statistical guidance (read the median rather than the mean), giving the agent concrete direction on how to interpret results. This fully covers when-to-use vs alternatives.

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