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

Annotations already declare readOnlyHint, idempotentHint, and closed-world, so the safety profile is covered. The description still adds non-obvious context: no external HTTP calls, no auth required, and deterministic compile-time adapter constants, which tells the agent results can be cached and need no credentials.

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?

Three sentences, zero padding, and the core purpose plus returned fields are front-loaded before side effects and routing guidance. Every sentence carries distinct information.

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?

An output schema exists, so return-value documentation is not required, yet the description still sketches the payload shape. Combined with explicit side-effect and sequencing notes, the definition is complete for a single-param lookup tool.

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 single 'channel' parameter is well documented with examples and the platform-prefix caveat. The description adds no additional parameter meaning, so the baseline of 3 applies.

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?

Names a specific verb+resource ('Return static per-channel metadata') and enumerates exactly what comes back: character limits, Markdown support flags, tag vocabulary, CTA placement rules. It also implicitly separates itself from the post_* siblings by scoping itself to static, pre-composition data.

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?

Explicit sequencing guidance: 'use channel_hints before composing a variant body' and 'use post_publish or post_schedule once you have a valid variant.' Names the alternatives and the condition that selects them, so an agent can route correctly without inference.

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