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

Annotations already convey that this is a mutating, idempotent, non-destructive operation. The description adds valuable behavioral context: authentication methods, the non-guest restriction, the escrow-funding prerequisite, preferred parameter usage, and the REST endpoint. This goes beyond what annotations alone provide.

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 compact and front-loaded: it leads with the core purpose, then covers prerequisite, authentication, parameter preference, and guest restrictions. Each sentence is informative, though the REST endpoint is slightly redundant with the input-schema's 'REST body + session id' note.

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 covers the important call context well: what action to take, prerequisites, auth, non-guest restriction, and preferred parameter choice. The main gap is that it does not directly mention how to create or source the escrow via sibling tools like data_session_fund or data_session_funding_package, and it doesn't describe the success response.

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?

Only session_id has a real schema description; open_tx_hash and proof_escrow_id are mostly bare. The tool description compensates by explaining that these represent a buyer-funded proof escrow and that open_tx_hash is preferred over proof_escrow_id. That is meaningful semantic guidance not present in the schema, though it still leaves some ambiguity about how those values are obtained.

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 tool's purpose: buying per-query access to live data listings by attaching a buyer-funded proof escrow to an opened data session. It names the concrete verb and resource, and distinguishes itself from data_preview by framing that tool as the free first taste.

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 strong usage context: requires an opened data session, an agent API key, a buyer-funded proof escrow, and explicitly says it is not guest-callable. It also points users to data_preview for a free trial. It does not explicitly contrast with data_session_fund or data_session_funding_package, so it stops short of a perfect usage guide.

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