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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description still earns credit by adding data-freshness context that annotations cannot express: results come from 'stored snapshots, no Meta call', telling the agent figures may be stale and that the call is cheap and offline. It does not explain behavior for an unknown or unlinked competitor id.

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?

Three short sentences, front-loaded with the action and followed by the result shape and the data-source caveat. Nothing is wasted, though 'the per-metric differences the portal shows' is slightly circular phrasing.

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 does the work of telling the agent what comes back: competitor and own account side by side plus per-metric deltas. For a one-parameter read tool with full annotation coverage this is nearly complete; only error/empty-competitor behavior is unaddressed.

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 baseline is 3. The schema's param text is just 'Numeric id.', but the description's 'compare against one competitor' usefully implies the id identifies that competitor rather than an account or post; it adds no format, validation or lookup hints beyond that.

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 first sentence states a specific verb and scope: compare against exactly one competitor. It implicitly separates this from list_competitors and get_competitor_leaderboard via the 'one competitor' framing, though it never names those siblings explicitly.

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 only implied: reach for this when you need a head-to-head for a single competitor. There is no explicit when-not guidance and no pointer to the leaderboard/overview tools for the multi-competitor or aggregate case, so the agent must infer the routing itself.

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