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

Beyond the readOnly/idempotent/harmless hints in annotations, the description discloses that no API key is required, that only public metadata is returned and corpus rows are never exposed, and that the optional question is echoed back. It also surfaces the session-routing default. No contradictions with 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 compact and front-loaded with the most decision-relevant fact (no API key needed), then lists outputs, then covers parameters and the follow-up purchase path. Every sentence contributes distinct information, and there is no fluff or redundant restating of the schema.

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?

There is no output schema, so the description correctly takes on the burden of naming the return fields (title, price, up to 3 sample questions, summary excerpt) and explicitly stating the important boundary condition (public metadata only, never corpus rows). With only two optional parameters and no output schema, the description leaves no meaningful gaps for successful invocation.

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?

The input schema already describes both optional parameters at 100% coverage. The description adds extra value beyond the schema by imposing the ≤300-character limit on question, noting the echo behavior, and explaining that slug defaults to the routed session's listing. This improves practical usage without breaking the baseline.

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 clearly states a specific action (preview a listing) and resource (public metadata of a paid data listing), enumerating expected outputs: title, price, up to 3 sample questions, summary excerpt. It also distinguishes itself from paid query tools by explicitly saying 'never corpus rows' and by referencing the paid workflow that follows.

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 says 'No API key needed — call this now' and explains the default resolution (routed session listing or explicit slug). It also provides a concrete purchase/query path — register → data_session_fund → data_session_query with sandbox_receipt=true — so an agent knows when to use this tool versus the paid alternatives.

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