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

Annotations already cover read-only, idempotent, closed-world, so the description's additive value is "a fixed dataset returned whole, with no paging" — a genuinely useful operational fact that prevents an agent from hunting for pagination params. The field enumeration is somewhat redundant with the output schema, which keeps this short of a 5.

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-loaded with verb + resource, then routing guidance, then a behavioral caveat — a logical order with no filler sentences. The middle clause packing ~7 returned fields is dense but still readable.

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 single-optional-param, read-only list tool with an output schema and full annotation coverage, nothing an agent needs is missing: scope, filter behavior, no-paging semantics, and the alternative tool are all stated.

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 enum param already says "Omit for all platforms." The description only echoes this with "(or one platform's)," adding no format, default, or edge-case detail beyond the schema.

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 ("List every supported social media placement") and immediately names the returned data (frame size, aspect ratio, safe-area insets, usable box, source URL, CSV/JSON/DOI links). It is clearly distinguished from get_social_media_placement in the same breath, so an agent can pick between them without opening either 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?

Explicit routing: "Use this to browse, compare platforms, or find a placement id; use get_social_media_placement when you already know the id and also need a crop/letterbox plan." Both the when-to-use and the named alternative with its selection condition are present.

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