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

Annotations already declare readOnlyHint/idempotentHint, so safety is covered; the description earns credit by disclosing the return shape (which rules are included) and the non-obvious `null` semantics, including the special case where `null` for `first_comment` means the platform takes none. It repeats 'Read only' from annotations, which adds nothing, but the null-handling note is genuine value.

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 tight sentences, front-loaded with the returned fields, then the usage rationale, then the null semantics that would otherwise confuse an agent. Nothing is padding except the redundant 'Read only' tail.

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, and the description compensates by enumerating the returned rule fields and explaining the `null` convention. Combined with a fully documented single optional parameter, an agent has everything needed to call and interpret this tool.

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% and the single `platform` parameter is fully documented there, including case-insensitivity and the list_accounts cross-reference. The description adds no meaning about the parameter, so the 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?

The first sentence names the resource and enumerates the exact facts returned (caption length, media counts, media requirement, first comment). No sibling among the post/plan/publish tools does anything similar, and the description makes that distinction obvious 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?

It gives a clear trigger: read these rules before writing for a platform you are not sure of, rather than learning from a refused post. There are no competing alternatives to name, but it also never states when the lookup is unnecessary (e.g. for a platform you already know), so it stops short of full when/when-not coverage.

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