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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and the description adds genuinely new behavior: the 410 response for removed/expired listings, the body_untrusted marker, that the call is free, and that likes are per-address-per-day and not a ranking signal.

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?

The resource and its identifiers are front-loaded and there is almost no filler, though the sentence is dense and the likes explanation sits mid-paragraph rather than being clearly separated as response interpretation guidance.

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 a single fully documented parameter, no output schema, and full annotation coverage, the description fills the remaining gaps: what the response represents, the gone/expired error state, the meaning of likes, and the untrusted-content handling instruction.

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 schema itself documents the 26-character id with an example. The description restates the same 26-character fact and adds only the provenance of the id, so it does not meaningfully extend what the schema already provides.

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 the specific action and resource ('One listing by id') and anchors it to a concrete endpoint contract ('what GET /p/{id}.json returns'). Referencing create_post and search_posts as the producers of the id implicitly distinguishes this read-one tool from the create and search siblings.

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?

It establishes the precondition (you need a 26-char id, obtained from create_post or search_posts) and the failure case (410 for removed or >30-day-expired listings). There is no explicit 'use search_posts instead if you only have a query' exclusion, so routing guidance is clear but not fully enumerated.

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