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

Annotations already cover read-only/idempotent/non-destructive safety, but the description adds genuinely useful context beyond them: no authentication required, the response is a range (not a commitment), and it reports how many creators sell the format and when the data was read. That freshness/coverage disclosure is exactly the kind of behavioral detail annotations cannot express.

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?

'No account needed' is well front-loaded, but the core sentence is a long run-on that buries the subject ('The all-in price range ... and that range times the number of posts ... with how many creators ...') and forces re-reading. The plan-vs-range caveat is useful but the overall packaging is dense rather than economical.

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?

There is no output schema, so the description correctly takes on the burden of describing the return: price range, creator count, and read timestamp. It also covers the auth model and the range/plan distinction. The only gap is that it never states a currency or unit for the range, leaving the numeric output under-specified.

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, but the description adds interpretation: 'posts' scales the per-post range (the range times the number of posts) and the format options are glossed as original post, quote repost, or thread. This explains how the two parameters combine to form the result, which the schema alone does not.

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 concretely defines the output: an all-in price range a brand pays per post in a given format, multiplied by the number of posts, plus creator count and data recency. It also cleanly distinguishes itself from a real 'plan' (which names creators and dates). The verb itself is implicit (the title says 'Estimate'), making it slightly less crisp than a 5, but the resource and scope are unmistakable.

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?

'No account needed' states the key usage precondition for this guest tool and contrasts it with a plan that requires an account/key. However, it never routes the agent among the actual siblings (inventory, resolve_audience, guest_status) or explains when to reach for a guest estimate versus an authenticated plan. Usage is implied rather than spelled out.

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