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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description adds crucial behavioral context: no authentication is required, the tool never returns corpus rows, the question parameter is merely echoed back, and the response is limited to public metadata. It also discloses the monetization context by routing onward to the purchase flow. None of this contradicts the 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?

Four dense sentences, each earning its place: the no-auth hook, the core scope limitation, the parameter behavior, and the purchase sequence. The essential facts are front-loaded, and there is no redundant filler or restatement of the title.

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 read-only, idempotent tool with two optional parameters and no output schema, the description is complete: it enumerates the return contents (title, price, up to 3 sample questions, summary excerpt), the data scope boundary, auth requirements, parameter routing, and follow-up steps. The only minor gap is the failure mode when no slug and no routed session exist, which is negligible at this complexity.

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 100%, and both parameter descriptions are already informative — slug's default-to-routed-session behavior and question's echo-back behavior are fully documented in the schema. The description restates these facts ('Defaults to the routed session's listing (or pass slug). Optional question (≤300 chars) is echoed back') without adding meaning beyond the schema, so the baseline 3 applies.

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: it gives a free 'taste' of a paid data listing, returning title, price, up to 3 sample questions, and a summary excerpt. It explicitly distinguishes itself from the paid query path by declaring 'PUBLIC metadata only, never corpus rows,' so an agent can tell it apart from sibling data_session_query without opening that tool.

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 opens with 'No API key needed — call this now,' signaling exactly when to invoke it, and clarifies the routing behavior ('Defaults to the routed session's listing (or pass slug)'). It then names the paid alternative path explicitly — 'register → data_session_fund → data_session_query (sandbox_receipt=true)' — giving the agent a clear condition for when this tool is enough versus when the buy-flow siblings are required.

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