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

Beyond annotations, which only set readOnlyHint=false and openWorldHint=true, the description discloses access tiers, success preconditions, pay-per-use costs, confirmation requirements, and content policy guardrails. This is substantial behavioral context that annotations do not provide.

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 description is dense and front-loaded, with every sentence adding relevant operational or policy value. Pricing, success conditions, and usage rules all earn their place without 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?

For a mutating X API action with no output schema, the description covers the essential invocation context: endpoint semantics, confirmation, access restrictions, and cost implications. It stops short of describing expected response shape or media handling, but the tool remains safely invocable.

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 only 25%, so the description must compensate. It adds meaning for confirm and in_reply_to_tweet_id, and warns about link costs, but leaves text and media_ids behavior implicit. Partial compensation, not complete.

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?

The description opens with a specific verb and resource — 'POST /2/tweets as a reply (in_reply_to_tweet_id)', making the tool's core action unmistakable. It also identifies the reply relationship explicitly, which separates it from siblings like create_post, quote, and create_thread.

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 provides concrete conditions for when this tool is allowed: replies to others succeed only if they @mentioned or quoted you, and self-replies are the intended thread mechanism. It also adds strong anti-spam and link-warning guidance, though it does not explicitly name alternative tools.

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