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

Adds real behavior beyond the annotations: nothing is published, the chat renders the original post above the reply, and Copy/Reply-on-X opens X's composer prefilled. That resolves the ambiguity left by destructiveHint=true, which would otherwise suggest a live write to X. It stops short of stating auth requirements or whether a prior draft is replaced or duplicated on re-invocation.

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 short sentences, front-loaded with what the tool does, then the non-posting behavior, then the trigger, then the style constraints. Nothing is redundant with the name or title.

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?

Two required params, full schema coverage, no output schema. The description covers what happens in chat, what the user sees, and the composition rules, which is everything an agent needs before calling it.

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 coverage is 100%, so both parameters are already documented as baseline. The description still adds constraint semantics the schema lacks: write in the user's voice, max 280 characters, no hashtags — guidance that directly shapes the `text` value.

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 ("Write a reply to a post on X") and immediately scopes it as a draft-only operation, so an agent can distinguish it from any send/post capability. No sibling tool competes for this action, and the outcome is concrete.

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 an explicit trigger ("whenever the user asks you to reply to, answer or respond to an X post") plus iteration behavior ("call it again with the revised text when they want changes"). Both the entry condition and the re-invocation pattern are spelled out rather than inferred.

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