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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds value beyond that by disclosing what data is returned (provenance, text evidence, device context) and what the tool deliberately does not do. It does not cover behavior on a missing or invalid id, which keeps this from 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?

Two short sentences with no filler; the positive scope statement is front-loaded and the exclusion follows it. Every clause earns its place.

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, the description's enumeration of returned fields is genuinely useful completeness work, and the annotations cover the safety profile. Gaps remain around id format and error behavior for a two-required-param lookup, but the essentials for calling it are present.

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 0% and the description never mentions either parameter. 'One captured ad' weakly implies that id identifies an ad, but the identifier format and the role of platform are left entirely to the schema's type/env constraints.

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 ('Read one captured ad') and enumerates the returned content (category provenance, text evidence, device context), which lets an agent distinguish it from search_ads and compare_ads. It stops short of naming the sibling alternatives explicitly, so it is clear but not fully differentiated.

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?

'Read one captured ad' implies single-item retrieval by platform+id, which is an implied usage distinction from search_ads. The only explicit boundary is the negative statement about advertisers and previews, which does not map to any sibling capability. No positive when-to-use guidance or prerequisites are given.

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