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

Goes well past the annotations: discloses that only the association is removed, that a no-op returns success (concretizing idempotentHint), that a nonexistent or cross-account tag_id is an error, and that WRITE-level access is required. This is exactly the mutation-safety context an agent needs.

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?

Four compact sentences, each carrying a distinct fact (scope, non-destruction, idempotency, error/auth semantics). The key constraint is front-loaded and there is no filler.

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?

Given a mutation tool with annotations, a fully described nested schema, and an output schema, the description covers everything else an agent needs: what is and isn't destroyed, success semantics for no-ops, error cases, and permission requirements.

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?

The nested schema already documents tag_id, post_id, and account_id, and the description adds meaning beyond that by stating the cross-account error condition and that the tag entity survives. It does not clarify the request wrapper or the relationship between account_id and post ownership in more detail, so not a 5.

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?

Specific verb plus resource: 'Detach a tag from an existing post by tag_id', immediately distinguishing it from add_tag and from any tag-deletion tool by clarifying the tag itself is not deleted. An agent knows exactly what this operation does.

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 conditions for use (you have a post and a tag_id association to break) and explicitly frames the no-op case, so the agent knows what happens when the association is already absent. It never names add_tag as the inverse alternative, so routing guidance is implied rather than explicit.

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