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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the mutation/non-idempotent profile is covered structurally. The description adds genuine context that the target must be an unpublished post and that the effect only manifests on Reel publication, but it says nothing about failure behavior on published posts or duplicate-call effects.

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 short sentences with the action and its key constraint front-loaded and no filler. The second sentence is vague enough ('Applies when it publishes as an Instagram Reel') that it could be tightened, but nothing is wasteful.

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?

For a small 3-parameter mutation with no output schema, the description covers the action, source of the sound, and the unpublished/Reel condition. It omits error handling, whether audioName is needed for correct rendering, and any confirmation of what the tool returns, leaving a modest gap for a write operation.

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% (postId, audioId, audioName all documented in-schema), so the baseline is 3. The description only reinforces that audioId comes from search_trending_audio and does not explain the optional audioName's display role or the exclusiveMinimum constraint beyond the schema.

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 ('Attach a sound ... to an unpublished video post') and names the sibling that supplies the sound (search_trending_audio), which differentiates it from other post-mutation tools. The trailing clause about Instagram Reels is slightly ambiguous but does not obscure the core action.

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?

Gives a clear precondition (the post must be unpublished) and an applicability condition (it publishes as an Instagram Reel), plus the upstream dependency on search_trending_audio. It stops short of stating what to do instead for non-Reel or already-published posts, so it is not fully exhaustive.

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