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

Annotations already mark the tool as read-only and idempotent, and the description adds substantial behavioral context: it requires a JSON body, returns a `{"message": "…"}` JSON object, is about 2 KB, and that streaming modes repeat the whole answer in every event, measured at 177 KB. This goes well beyond what annotations or schema convey.

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 dense but every sentence earns its place: differentiation from siblings, JSON body requirement, parameter values, mandatory response mode, return format, size, streaming caveat, and the tool's limitation. The most important guidance is front-loaded in the first sentence and the warning is placed prominently.

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 4-parameter tool with full schema coverage, the description is complete: it explains what the tool does, how to obtain the required ID, how to invoke it safely, what the output looks like, and what it cannot do. There are no critical gaps an agent would need to guess at.

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%, so the baseline is 3. The description adds meaningful value by clarifying that `search_id` must come from a prior search call and by warning that `response_mode` should be NON_STREAMING with quantitative evidence. It does not add much beyond the schema for `language` and `detail_level`, but the critical parameter guidance is present.

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 states a specific verb and resource: 'Explain a result set you already fetched.' It clearly distinguishes this tool from the search endpoints by name ('Unlike the three search endpoints') and explicitly states it 'cannot run one.' An agent can immediately tell what this tool does and what it is not for.

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 gives direct guidance: use `response_mode: NON_STREAMING`, explains why COMPLETE/INCREMENTAL modes are impractical ('a tool call cannot consume a stream incrementally anyway'), and clarifies the tool only explains existing searches, not runs them. It also names the exact search endpoints that produce the required `search_id`. This is explicit and actionable.

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