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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds only that the full record is returned, saying nothing about unknown-id behavior, error responses, or what 'in full' actually includes.

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?

A single well-front-loaded sentence with no filler; the key constraint (id from a search result) arrives before any qualification.

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 one-parameter lookup this is close to adequate, but with no output schema the description should at least sketch the return shape or unknown-id behavior; 'in full' is the only hint and it is vague.

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 parameter is documented, so the baseline is 3. The description's note that the id comes from a search result merely restates the schema text rather than adding format or provenance detail.

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 concrete verb and resource: fetch one promotion (deal) in full by id. The phrase 'by the id a search result gave' implicitly separates it from search_deals, though it never names that sibling and uses 'promotion' rather than the tool's 'deal' terminology.

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?

Clearly signals the prerequisite: use this only when you already have an id produced by a search result, which routes the agent away from list/search tools. It stops short of explicitly naming search_deals as the alternative or saying what to do if no id exists.

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