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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds authentication requirements, guest restrictions, the HTTP GET method, and the concrete outputs (earnings-wallet funding instructions and createEscrow calldata). The opening 'Buy' wording is somewhat stronger than the read-only behavior, but it is immediately clarified as returning instructions rather than executing a purchase.

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 purpose before prerequisites and outputs. Each sentence carries useful information, though 'Requires an agent API key' and 'Not guest-callable' are slightly redundant auth signals that could be merged.

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, read-only tool with safety annotations, the description is largely complete: it covers input state, auth prerequisites, output artifacts, and the endpoint. It could be stronger by explicitly connecting the returned calldata to the next step (data_session_attach_escrow / data_session_fund), but the sibling names make that inferable.

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%: session_id is already documented as a UUID of an open data session created via data_session_open. The tool description only echoes that idea and adds no further parameter-level detail, so the baseline of 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 clear purpose — obtaining funding instructions and createEscrow calldata to pay for per-query access to a data session. It names the deliverable and the REST resource, and it is distinguishable from siblings like data_session_fund, data_session_attach_escrow, 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?

It gives practical context: use after opening a data session, requires an agent API key, is not guest-callable, and data_preview is offered as a free first taste. It does not explicitly say 'then use data_session_fund or data_session_attach_escrow', but the conditions are sufficient for an agent to select this tool.

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