Validate a thread

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

Annotations already declare readOnly/idempotent/non-destructive, and the description reinforces that with an explicit 'Side effect: none' plus the registry acceptance rule, which is real added context. It also discloses the return shape (flags plus an issue list with per-post evidence) and the specific rule set applied, though it doesn't say how severe flags are surfaced or whether validation is partial on failure.

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?

Front-loads the most decision-relevant fact (no saving) and packs the rule list into one dense sentence with no filler. Slightly run-on, but every clause carries information an agent would otherwise have to discover by calling it.

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?

Single-parameter, non-destructive tool with no output schema, and the description covers the checks performed, that nothing is persisted, and the rough return contents — enough to call it correctly. It stops short of describing the flag vocabulary or how issues map to posts, which is a minor gap given no output schema exists.

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% and the posts description already covers ordering and the links-on-final-post convention, so the baseline is 3. The description adds meaning the schema lacks — the 280-char per-post limit and that 'post 1' is evaluated specifically for hook quality — which clarifies what the parameter is judged against.

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 ('run the per-post evidence check on a draft thread') and enumerates exactly what is checked: 280-char limit, 25-post limit, empty posts, hook quality, links-on-final-post. It explicitly separates itself from draft_thread by declaring it saves nothing, so an agent can distinguish it from draft_thread/post_thread without opening a schema.

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?

'WITHOUT saving anything' plus 'the registry only accepts drafts made with draft_thread' tells the agent this is a pre-flight check against a draft, not a creation or publishing step. It gives clear context but never explicitly names when to prefer post_thread or schedule_thread over this, or states a required call order beyond the registry caveat.

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