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

Annotations already declare readOnlyHint=true, so 'Pure analysis. Writes nothing.' reinforces rather than reveals. The real added value is the enumeration of what is actually checked (length, media requirements, hashtag ceilings, link clickability, YouTube titles, PII/prohibited content), which goes well beyond the annotation surface; missing are error behavior or whether results are per-platform verdicts.

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?

Two sentences, front-loaded with the concrete list of checks and closed by the read-only guarantee. Every clause carries information; no filler or repetition of the tool name.

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 does important work by naming the checks, which implies what the result covers, and it resolves the ambiguity of a nested platformMeta object by scoping the tool to a caption-level check. It could go further by indicating whether results are returned per platform with pass/fail detail.

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%, with title, mediaUrlsCount, hashtags and platforms all documented in the schema itself. The description's mentions of YouTube titles and media requirements map directly onto those existing schema descriptions, adding little beyond them; the nested platformMeta object remains unexplained in either place.

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 ('Check') and resource (a caption against each target platform's posting rules) and enumerates the exact rule categories checked. It is clearly distinguishable from the write-oriented siblings like sprkly_schedule_post or sprkly_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?

'before scheduling' gives a clear usage moment, and the scope ('each target platform') tells the agent this is a pre-flight check rather than a one-shot lint. However, it never explicitly names alternatives (e.g., use schedule_post once validation passes) or states when not to use it, so it stops short of full routing guidance.

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