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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context beyond them: the authorization model (merchant-only unless public) and the shape of what comes back (commission settings, cookie duration, partner count, status, timestamps).

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 short sentences, front-loaded with the action, then the return payload, then the access caveat. No filler and nothing is buried.

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?

With no output schema, enumerating the returned fields is the right compensating move, and the access rule covers the main failure mode. Minor gaps remain around not-found/unauthorized error behavior, but the definition is adequate for a simple single-resource read.

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 single program_id parameter is fully documented in the schema, including an example format (prog_abc123), so schema coverage is 100%. The description only restates "by ID" and adds no lookup-source or format guidance beyond that, which makes the baseline 3 appropriate.

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?

"Get full details for a single affiliate program by ID" gives a specific verb (get), resource (affiliate program), and scope (single, by ID). That scope immediately differentiates it from list_affiliate_programs and discover_affiliate_programs, which operate on collections.

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?

The description states the access condition explicitly — usable by the program merchant or by anyone if the program is public — which tells the agent when the call will succeed. It stops short of naming siblings (e.g., use list_affiliate_programs to find an ID first) or stating a when-not condition.

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