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

Annotations already flag destructiveHint=true and idempotentHint=false, and the description reinforces this with concrete consequences: previous content is replaced and not kept, omitted fields are preserved, empty array removes media, null reschedules back to DRAFT. That is well beyond what the annotations convey.

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 key in-place/no-recreate point is front-loaded and the per-field semantics are tightly packed. The trailing French sentence duplicates the same content, which is useful for bilingual users but redundant padding for an agent, costing it the top score.

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 mutation tool with no output schema, the description covers what can go wrong (refusal on published posts), what is destroyed (replaced content), and how each optional field behaves when omitted or set to null/empty. Nothing an agent needs to call it correctly is missing.

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?

Despite only 67% schema coverage, the description documents each optional field's replacement semantics (content string vs thread array replacing all text, account_ids replaces targets, media_uuids replaces with order preserved and empty array clears, scheduled_at null unschedules). It adds interpretation the French schema descriptions alone do not fully surface for an English-reading agent.

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?

A specific verb ('Modify') plus resource ('an existing post') and an explicit scope qualifier ('IN PLACE'). It distinguishes itself from delete_post/create_draft_post siblings by stating that recreating would lose history, so an agent can pick it over the alternatives without inspecting schemas.

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 explains why to use update-in-place over delete/recreate and gives a clear negative condition ('Refused when the post is already published or currently publishing'). It stops short of naming a sibling tool or a pre-fetch step, so it is strong context without full explicit routing.

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