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

Annotations declare readOnlyHint=true and openWorldHint=true, and the description adds valuable behavioral context beyond them: it states the operation is free ('does not charge credits'), that returned criteria are 'already merged', and that stale Sources should be reported before using their mentions. This is meaningful for correct agent behavior and does not contradict annotations.

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?

The description is longer than minimal, but every sentence earns its place: the first sentence is a dense specification of the return payload, the next two give diagnostic use cases, and the last adds cost information. It is front-loaded with the core purpose and contains no filler.

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 simple read-only tool with one parameter, no output schema, and an explicit enumeration of returned fields, the description is complete. It explains what the tool returns, when to use it, and the cost behavior, so an agent can invoke it correctly without additional context.

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 `id` parameter is fully documented in the schema, including the 404 vs 403 behavior. The description adds no parameter-level detail, so it earns the baseline for high schema coverage.

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?

The description uses a specific verb ('Get') and resource ('keyword'), and enumerates the exact response contents, distinguishing it from siblings like get_keyword_results and get_keyword_events. It frames the tool as the diagnostic view for 'why did/didn't this get caught?', which clearly identifies its unique purpose.

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 explicitly tells the agent when to use the tool: to answer 'why did/didn't this get caught?' and to report a stale Source before answering from mentions. It does not explicitly name alternatives or state when-not-to-use, but the use cases are clear and actionable.

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