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

Annotations already mark the operation as non-read-only, non-destructive, and idempotent. The description adds valuable behavioral constraints beyond those: authentication requirements ('Authorization: Bearer or X-API-Key'), guest-call restrictions, and the fact that this is a paid per-query purchase. This is meaningful supplementary context with no contradiction.

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 opens with the core value, then covers auth, parameters, constraints, and endpoint in a few short sentences. There is no filler or repetition of schema details.

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 with no output schema and three parameters, the description covers authentication, prerequisites, parameter options, free alternative, and the REST route. It does not explain what response to expect or explicitly warn that one escrow identifier might be required if both are absent, but the provided context is strong enough for correct invocation.

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%, so the description must compensate. It does name open_tx_hash and proof_escrow_id and indicates preference ('open_tx_hash preferred'), and it ties session_id to 'an opened data session.' However, it does not explain the format or origin of the escrow identifiers beyond their names, leaving some semantic work undone.

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 action with a clear resource: 'Attach a buyer-funded proof escrow ... to an opened data session.' It also names the exact REST endpoint and specifies the two acceptable escrow identifiers, making the tool's purpose unmistakable and distinct from siblings like 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 context for when to use the tool: after opening a data session and when purchasing paid access, with data_preview offered as the free alternative. It also states prerequisites and restrictions: requires an agent API key, is not guest-callable, and needs an already opened session. It could have explicitly contrasted with data_session_fund but still gives adequate routing guidance.

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