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

Annotations already mark this as non-read-only, idempotent, and non-destructive. The description adds meaningful financial context: this is a paid purchase at a fixed USDC price, and funding is executed by the platform, alerting the agent to monetary side effects beyond what annotations 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?

Three sentences, each carrying a distinct piece of information: the action, the specific listing and price, and the follow-up capability. It is compact and front-loaded, though 'first taste free' is slightly promotional rather than purely instructional.

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?

The essential context for invocation is present: the source of session_id, the cost per query, the free preview alternative, and the enabled next step data_session_query. With no output schema, a clearer description of the return or confirmation state would improve completeness, but the description is still sufficient for correct use.

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?

There is only one parameter, session_id, and the schema already documents it fully as the UUID of a data session from data_session_open. With 100% schema coverage, the description does not need to add parameter detail, and it does not.

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 names the operation as buying per-query access to a specific listing (pmnews at 0.01 USDC/query) and states the consequence: platform-executed funding that enables data_session_query. This clearly separates the tool from the free data_preview step and the subsequent query step, so an agent can identify what the tool does without opening its schema.

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 routes new users to data_preview for a free taste and states that after funding the session you can call data_session_query. This provides useful ordering guidance, though it does not explicitly mention when to prefer data_session_funding_package or data_session_attach_escrow instead.

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