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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructiveness, so the safety profile is covered. The description adds the per-call cost, which is real behavioral context an agent cannot get from the annotations, but omits anything about auth, rate limits, or side effects.

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 compact sentences, front-loaded with the core purpose before the cost and sourcing details. The terse 'Paid, about $0.004 per call' fragment earns its place as a decision-relevant fact.

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 an output schema present, the description needn't document return values, and it covers purpose, sourcing, and cost adequately. It is essentially complete for a one-parameter read tool, though a hint about how to interpret the audience-match result would fully close the loop.

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 coverage is 100% and the single parameter is already typed, so the baseline is 3. The description adds provenance value the schema lacks: the ID must come from list_saved_keywords, which tells the agent where to source it rather than just its type.

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 ('looks at who currently ranks for a keyword') plus the decision it supports ('judge whether its searchers match your audience'). It also names adjacent siblings (list_saved_keywords, save_keywords, research_keywords), so an agent can place it relative to alternatives without opening schemas.

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?

Gives concrete invocation context ('Pass a savedKeywordId from list_saved_keywords') and a cost signal ('Paid, about $0.004 per call') that helps an agent decide whether to call it. It stops short of explicit when-not-to-use or exclusion rules, so it lands just below the top.

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