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

Annotations only give the safety profile (not read-only, not idempotent, not destructive, open world). The description adds substantial context beyond that: it discloses the atomic mutate that creates assets and links in one operation, the failure mode (no orphaned unlinked asset), and the cost behavior (free). It omits a warning that, being non-idempotent, re-runs may create duplicate sitelinks, which is a notable gap.

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 tightly written sentences, front-loaded with the definition of sitelinks before the benefit and atomicity details. Every clause carries information; there is no filler or repetition of the title.

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 complex mutation with nested objects and no output schema, the description covers the key behavioral essentials (atomicity, cost, validateOnly scope). It could be stronger by noting what the tool returns or how re-invocation behaves for a non-idempotent create, but nothing critical to correct invocation is missing.

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 60%, so the description must partly compensate. It reinforces validateOnly semantics (validates the whole atomic operation) but adds little on the sitelinks array shape or the extraFields escape hatch beyond what the schema already documents. Baseline 3 is appropriate given the schema does most of the work.

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 ('Add sitelinks ... to a campaign') and disambiguates what sitelinks are with concrete examples (/pricing, /security). It is clearly distinguishable from siblings like add_callouts or add_keywords. No ambiguity about the operation.

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 motivates use (raises CTR/Quality Score, lowers CPC) and mentions that validateOnly checks the whole operation, which implies a dry-run-first workflow. However, it never states when NOT to use it or names an alternative sibling (e.g. add_callouts), so usage guidance is implied rather than explicit.

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