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

Goes well beyond readOnlyHint/openWorldHint: discloses that only the last 20 posts are aggregated, that results are numeric only, that X depends on a key being enabled, and the full billing model (invalid input free, not-found uncharged, $0.02 per successful call via x402 USDC on Base with the _meta payment key). That payment and partial-failure-fee behavior is exactly the context an agent cannot get from the schema or annotations.

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-loads purpose and output scope, then payments, and no sentence is filler. The final pricing sentence is dense with x402/_meta detail but each clause is operationally necessary for a paid tool, so the length is justified though slightly packed.

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 return-shape burden and does so: it lists every returned metric and its averaging window, plus the null-return condition (not found / no match). Platform support, cost, and payment mechanics are all covered, leaving nothing an agent needs before calling.

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 coverage is 100%, so the baseline is 3; the description adds real meaning beyond it by clarifying that the call targets exactly one account and by caveating that the 'x' enum value only works when its key is enabled — a constraint absent from the schema's flat enum list. Handle formatting is left to the schema, so it stops short of 5.

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?

Names a specific resource (audience & engagement stats) for a specific scope (one account on TikTok/Instagram/YouTube/Threads, or X) and enumerates exactly what is returned: followers, following, posts, and average likes/comments/views over the last 20 posts plus engagement rate. The explicit negatives ('No follower names, no post text') separate it from follower-listing siblings like tiktok_followers and from post-content tools like x_posts.

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?

'Influencer vetting and benchmarking' gives a clear use context, and the 'numbers only / no follower names / no post text' framing implicitly steers agents to other tools for raw lists or content. What is missing is an explicit named alternative (e.g. social_accounts to resolve a handle, tiktok_followers for follower lists), so the routing guidance stops short of the top tier.

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