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

Annotations already provide readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context beyond these: it requires an agent API key, is not guest-callable, prefers open_tx_hash over proof_escrow_id, and exposes the REST endpoint. This helps the agent anticipate authentication and parameter preferences.

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 concise and information-dense, with the core purpose front-loaded and supporting details in short follow-up sentences. The REST endpoint and auth requirement each earn their place, though the opening marketing phrase could be trimmed without loss of functional meaning.

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 3-parameter tool with no output schema, the description provides the key workflow context: open a session, have funded proof escrow, attach using the preferred hash. It includes authentication and REST details. Missing are explicit notes about response behavior and whether the escrow is consumed, but annotations already cover idempotency and non-destructiveness.

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 only 33%, with session_id documented. The description partially compensates by explaining that open_tx_hash is preferred and proof_escrow_id is an alternative, and by embedding the session_id in the REST path. It does not fully define what proof_escrow_id represents or how the two alternatives interact, so the added value over the schema is moderate.

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: 'Attach a buyer-funded proof escrow ... to an opened data session.' It also clarifies the broader purpose, 'Buy per-query access to live data listings,' and distinguishes this from data_preview. The REST endpoint further anchors the operation.

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 provides clear context for when to use this tool: after opening a data session, with an agent API key, and not guest-callable. It also hints at data_preview as the free alternative. However, it does not explicitly contrast with sibling data_session_fund or data_session_funding_package, so a direct when-not-to-use comparison is missing.

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