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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description adds meaningful behavior beyond them: Google Ads proximity fields are immutable so update is an atomic remove+add, 'replace' deletes ALL existing targets, and confirm=false is a dry-run. It doesn't discuss rate limits or auth, but the added context is substantial.

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 the key differentiator before the action list, and the bullet structure maps cleanly to actions. It is dense and the points JSON example adds length, but every element carries semantic value for a mutation tool.

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 10-parameter mutation tool with an output schema present, the description covers the action taxonomy, parameter formats, dry-run safety, and the immutability constraint that changes expected behavior. Return values are handled by the output schema, so nothing an agent needs 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 0%, so the description carries the full burden and does so well: it defines action values, units ('KILOMETERS' default vs 'MILES'), radius semantics, the points JSON batch format with an example, and where to obtain criterion_id. Only customer_id/campaign_id are left unexplained, which is acceptable given their obviousness.

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+resource (manage a campaign's proximity/radius targeting) and immediately distinguishes it from siblings, noting these are 'the radius targets that get_campaign_targeting reads but set_campaign_targeting CANNOT change.' An agent can route to it without opening any 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?

Explicitly names the two sibling tools and the exact division of labor between them, then enumerates the four actions (add/update/remove/replace) with the condition selecting each, including the edge case of clearing all targeting via 'replace' with no points.

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