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

Annotations indicate idempotentHint=true and destructiveHint=false, and the description does not contradict these. It adds behavioral context beyond annotations by specifying authentication requirements (Bearer or X-API-Key), the REST method (POST), and the billing aspect ('Buy per-query access'). It does not describe error handling or side effects, but the annotations cover safety and idempotency.

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 dense but well-structured, leading with the core purpose, then auth, then attachment details, then restrictions and endpoint. Every clause adds value—no filler. It is appropriately sized for a tool with three parameters and moderate complexity.

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 mutation tool with no output schema, the description covers the essential inputs, auth, endpoint, and alternative. It does not explicitly state what the response will be (e.g., success status or updated session), but given the sibling data_session_query and the purpose, an agent can infer the result. The lack of return-value info is a minor gap, but overall the description is fairly complete.

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% (only session_id has a description). The description compensates by clarifying the two escrow parameters: 'open_tx_hash preferred, or proof_escrow_id' — indicating they are alternatives and which is preferred. This adds meaning beyond the schema's bare types and defaults.

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 clearly states the action: 'Attach a buyer-funded proof escrow to an opened data session.' It specifies the resource (data session) and the object (escrow), and distinguishes from siblings like data_session_open and data_session_fund by focusing on the escrow attachment step. The phrase 'Buy per-query access' adds purpose context.

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 provides usage context by mentioning 'first taste free via data_preview' as an alternative for free access, and states prerequisites: 'Requires an agent API key' and 'Not guest-callable.' It implies you need an opened session (from data_session_open). However, it does not explicitly mention data_session_fund as an alternative for funding, or explicitly state when not to use this tool.

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