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

Annotations already cover idempotentHint=true and destructiveHint=false. Beyond these, the description discloses the auth mechanism (Bearer or X-API-Key), the guest restriction, the preference for open_tx_hash, and the REST endpoint — meaningful behavioral context that the annotations do not provide. No contradiction with annotations.

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?

Five short sentences, each earning its place: business context, auth requirement, core operation, eligibility exclusion, and REST endpoint. Slightly redundant front-loading (the buying/access framing could be trimmed), but overall compact and well-ordered.

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?

Everything needed to invoke the tool correctly is present: auth, eligibility, parameter preference, and session precondition. However, with no output schema, the description does not set expectations for the response (e.g., what confirms the escrow attach succeeded), and it does not link to the natural follow-up tool (data_session_query).

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 schema description). The main description partially compensates by explaining that open_tx_hash and proof_escrow_id are alternative escrow identifiers with a stated preference order. However, it does not define what a proof escrow is or how the agent obtains these values, leaving a semantic gap for the two optional parameters.

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 operation — 'Attach a buyer-funded proof escrow (open_tx_hash preferred, or proof_escrow_id) to an opened data session.' The verb+resource is unambiguous, and the workflow framing ('Buy per-query access... first taste free via data_preview') plus the REST endpoint make it easy for an agent to distinguish this from siblings like data_session_open, data_session_fund, 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 clear usage context: names data_preview as the free alternative ('first taste free'), states preconditions (requires agent API key, opened data session from data_session_open), and declares an exclusion ('Not guest-callable'). It does not explicitly contrast with the funding siblings (data_session_fund, data_session_funding_package), which is the main gap.

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