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

Annotations already provide idempotentHint=true, readOnlyHint=false, and destructiveHint=false. The description adds meaningful behavioral context beyond those: agent API key requirement, guest-call restriction, buyer-funded escrow requirement, and the preference for open_tx_hash. It does not contradict any annotation.

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?

Four concise sentences, each earning its place: purpose, auth requirement, attachment mechanics with preference, and REST endpoint. The main behavior is front-loaded; no filler or repetition.

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 three-parameter tool with no output schema, the description is nearly complete: it covers the required session_id context, the two funding-identifier alternatives, authorization, guest restrictions, and the REST endpoint. The only gaps are response/return behavior and what happens if the escrow is insufficient or invalid.

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 coverage is only 33%, so the description must compensate. It names open_tx_hash and proof_escrow_id and states that open_tx_hash is preferred, which is not present in the schema. It does not explain how to obtain these identifiers, but it adds enough meaning to shape invocation.

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 names a specific action ('Attach a buyer-funded proof escrow') and target resource ('an opened data session'), and sets the broader business purpose ('Buy per-query access to live data listings'). It also distinguishes itself from data_preview by calling out the free first taste, so an agent can tell this is the paid escrow-attachment step.

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 clear contextual guidance: use after opening a data session, requires an agent API key, is not guest-callable, and data_preview is the free alternative. It does not explicitly contrast itself with sibling tools like data_session_fund or data_session_funding_package, so it falls just short of full when/not guidance.

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