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

Annotations already establish readOnly and non-destructive behavior, yet the description goes well beyond them: it explains the null-versus-empty-object distinction, names the five networks where metricsAvailable is false, and discloses that Pinterest counters cover only the last 90 days rather than lifetime. These are exactly the semantics an agent needs to interpret results, and none are recoverable from annotations or schema.

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?

It is a single dense sentence that front-loads the core purpose before the edge cases, and each clause carries real information (null lifecycle, empty-object meaning, network caveats, 90-day window). The parenthetical network list and stacked idioms such as 'clicks (Pin clicks)' and 'linkClicks (clicks to the Pin link)' make it heavy, but almost nothing is filler.

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 largely does so, covering metrics, metricsAt, metricsAvailable and the daily history. The gaps are the shape of the daily history and how the days parameter relates to that history, which leaves it just short of fully complete for a metrics 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%, so the schema already documents both id (post id from list_posts or get_post) and days (1-365, default 90), which sets the baseline at 3. The description adds nothing about the days window, and its 90-day Pinterest note is network-specific rather than a clarification of the parameter, so it does not raise the score.

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 names a specific resource (platform-reported counters for every channel of a post) and enumerates the concrete fields returned (metricsAt, metricsAvailable, stored daily history). It is clear what the tool retrieves, though it never explicitly distinguishes itself from get_analytics_overview or get_channel_insights.

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?

There is no explicit when-to-use statement and no sibling alternative is named, even though get_analytics_overview and get_channel_insights sit in the same catalog. The only usage-adjacent information is the implicit hint that metrics is null until the first read, which tells the agent to expect an empty-then-populated lifecycle but not when to pick this tool.

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