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

Annotations already declare readOnlyHint=true, and the description reinforces with 'Pure analysis. Writes nothing.' It also exposes behavioral details beyond annotations, such as checking for 'PII or prohibited-content warnings' and 'whether links are clickable.' This adds value and does not contradict the 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?

The description is concise and front-loaded: it starts with the main verb 'Check' and lists checks in a readable comma-separated sequence. It ends with two short sentences ('Pure analysis. Writes nothing.') that reinforce safety. No redundant wording or filler; every sentence 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?

The tool has 6 params (2 required) and no output schema. The description explains what it checks, but not the exact return format (e.g., a list of issues, a boolean, or a report). Given the complexity and the absence of an output schema, describing the return type would improve completeness. Still, the purpose and scope are well-covered, and annotations provide safety context, so it is fairly complete but not perfect.

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%, so each parameter is already documented. The description references some parameters (e.g., 'required YouTube titles' for title, 'media requirements' for mediaUrlsCount, 'hashtag ceilings' for hashtags) but does not add new syntax or format details beyond the schema. It provides contextual mapping but not additional semantic depth, so the baseline of 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 description clearly states the tool's function: 'Check a caption against each target platform's posting rules before scheduling.' It lists specific checks (caption length, media requirements, hashtag ceilings, clickable links, YouTube titles, PII/prohibited content) and explicitly distinguishes it as 'Pure analysis. Writes nothing.' This differentiates it from mutation tools like schedule_post or draft_post.

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?

The description gives clear context: 'before scheduling' indicates when to use this tool, implying it is a pre-flight check. However, it does not explicitly name alternatives or state when not to use it. It could be improved by mentioning 'Use this before scheduling; if issues are found, address them before calling schedule_post.' Still, the timing guidance is useful.

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