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

Annotations already mark the tool as non-read-only, idempotent, and non-destructive. The description adds useful behavioral context beyond those: required auth headers, guest ineligibility, and the preference for open_tx_hash over proof_escrow_id. It does not contradict the 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?

Four compact, information-dense sentences with no filler. The purpose is front-loaded, and each sentence adds distinct value: free preview path, auth requirements, core attach action, guest restriction, and REST endpoint.

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 simple three-parameter mutation with no output schema, the description covers the action, prerequisites, endpoint, auth, access eligibility, and parameter preference. It does not describe the response or failure modes, but those are not essential given the annotations and sibling context.

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 is described in the schema. The description partially compensates by naming the two escrow identifier options and marking open_tx_hash as preferred, but it does not explain how to obtain proof_escrow_id or what distinguishes it beyond being an alternative.

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'), a specific target ('an opened data session'), and the commercial purpose ('buy per-query access to live data listings'). It also distinguishes itself from a sibling by noting the free alternative via data_preview.

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 usage context: use after opening a data session, requires an agent API key, and is not guest-callable. It explicitly points to data_preview for the free first taste, but does not discuss other alternatives like data_session_fund or when not to use this tool beyond the guest restriction.

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