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

Annotations already declare readOnly/idempotent/non-destructive, but the description still adds real value: it spells out the two issue categories (hard_limit vs style) and the exact semantics of `valid` being false when either is present. That is behavior an agent could not infer from the annotations alone.

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 sentences, front-loaded with the operation and its scope, then the routing advice, then the issuing semantics. No filler and no restatement of the tool name.

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?

Covers what is validated, that state is not mutated, when to call it, the account_id dependency, and how to interpret the two issue kinds. With an output schema present, the description does not need to enumerate return fields and correctly doesn't.

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?

The top-level schema has a single `request` object, but its nested properties carry extensive per-field descriptions, so the schema does most of the work. The description's only parameter-level contribution is reiterating that account_id is required for X to resolve the premium limit — which the schema already states — so it adds little beyond the baseline.

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 (dry-run validate) and resource (post content) plus the exact rule families checked: hard limits, counting rules, threading, banned words, media constraints. An agent can distinguish this from create_post/update_post immediately.

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 routes the agent: "Useful before create_post / update_post for any non-trivial content" names the sibling alternatives and the condition that selects this tool. It does not state when to skip validation (e.g. trivial single-line posts), which is the only gap.

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