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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, which the GET endpoint and calldata-returning behavior are consistent with. The description adds useful context beyond annotations: authentication header requirements, guest-call restriction, and the specific type of payload returned.

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 with no waste: purpose, prerequisites/auth, output and REST endpoint. Front-loaded with the main action, and every sentence adds value.

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 one-parameter tool with no output schema, the description is complete: purpose, prerequisites, auth needed, return type, and REST path are all covered. It does not explain what to do with the createEscrow calldata or cover error cases, but these are not critical for a simple read-only tool.

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 the schema already describes session_id as 'UUID of a data session you opened (from data_session_open).' The description adds no additional parameter semantics beyond what the schema provides, so baseline 3 is appropriate.

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 action and resource: 'Buy per-query access to live data listings' and 'Return earnings-wallet funding instructions and createEscrow calldata for an opened data session.' This clearly identifies the tool's role and distinguishes it from siblings like data_preview and data_session_query.

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?

Provides explicit context: first taste free via data_preview, requires an agent API key, not guest-callable, and assumes an opened data session. It names data_preview as a free alternative but does not explicitly contrast with data_session_fund or data_session_attach_escrow, which are the closest siblings.

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