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

Goes well beyond the annotations (which only declare non-readonly, non-destructive, open-world): it discloses credit consumption per page, a billing exception when a page adds no new posts, and async behavior where the call may return a job_id while loading instead of results. That is exactly the cost/async context an agent needs before calling a paid, non-idempotent-in-effect tool.

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 the action and scope in the first sentence, then layers prerequisite, return shape, cost, and metric semantics. The closing viral_score definition is tangential to invoking this tool and could be trimmed, but every other clause earns its place.

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 takes on the burden of describing return values and does so ('the whole result list with new_posts ... or the job_id while it loads'), plus cost implications and the meaning of viral_score. Nothing material is missing for an agent to call and interpret the result.

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% and the single job_id parameter is fully documented as coming from find_viral_posts, matching the description. The description adds no format, lifetime, or reuse guidance for job_id beyond what the schema already says, so baseline 3 applies.

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?

States a specific verb and resource ('Adds the next page of results') scoped to a named sibling operation ('a finished find_viral_posts search'), which separates it cleanly from find_viral_posts (start a search) and get_viral_results (retrieve results). An agent can pick this tool without opening the schema.

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?

Explicit trigger is given: 'Use it when the first page was not enough,' and the 'finished ... search' qualifier rules out calling it on an in-flight job. It does not explicitly compare against get_viral_results or state what to do once pages are exhausted, so it stops short of full when/when-not routing.

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