Draft a thread

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

Adds substantial behavioral context beyond annotations: the draft registry is in-memory (lost on restart), returns a draftId and validation report, and that post/schedule tools will reject undrafted posts with an error naming the exact text. This clarifies statefulness, side effects, and error behavior, consistent with the non-read-only, non-idempotent annotations.

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 dense but well-structured sentences: the first front-loads the core action and registry behavior, the second covers the downstream rejection consequence. Every sentence adds necessary information with no filler or redundancy.

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 stateful draft tool with no output schema, the description adequately covers registry lifetime, return values (draftId and validation report), and downstream error behavior. It does not elaborate on what the validation report contains or the specific validation rules, but that is a minor gap given the sibling validate_thread likely handles validation details.

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%, and the schema already documents the only parameter 'posts' including ordering and convention about links on the final post. The description adds no parameter-specific details beyond what the schema provides, so the baseline score of 3 is appropriate.

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?

Starts with 'Validate a thread AND register the validated posts in the in-memory draft registry', a specific verb and resource that clearly distinguishes this tool from validate_thread (which presumably only validates) and from post_thread/schedule_thread (which reject undrafted posts). The mention of sibling rejection further clarifies its unique role.

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?

Explicitly states that post_thread/schedule_thread reject any posts array that was never drafted, implying this tool must be used before those. It also notes the draft is lost on restart and must be re-drafted before finalizing. However, it does not explicitly contrast with validate_thread (e.g., when to prefer one over the other), leaving a minor gap in alternative guidance.

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