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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds substantial behavioral context beyond that: it requires an agent API key, executes platform-side funding for a sandbox wallet minted at register, lists the underlying operation flow (approve + createEscrowWithProof + attach), is testnet-only, and has no REST analogue. No contradiction with annotations exists.

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 dense but front-loaded with the core purpose in the first sentence. Every subsequent sentence earns its place by conveying auth requirements, platform execution details, environment restrictions, an alternative tool, and a REST caveat. It is slightly packed for a single description, but all content is relevant.

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?

Given a single required parameter, 100% schema coverage, and helpful annotations, the description is complete for invocation: it identifies the required session_id, the auth mechanism, the environment, the alternative funding path, and the fact that this is not guest-callable. No output schema exists, so return-value details are not expected.

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 100%: the single session_id parameter is already documented as 'UUID of a data session you opened (from data_session_open).' The tool description references data sessions but does not meaningfully add parameter-level detail beyond what the schema already provides. Baseline 3 is appropriate.

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 opens with a specific verb and object: 'Buy per-query access to live data listings.' It clearly distinguishes itself from closely related siblings by contrasting with data_preview (free taste) and data_session_funding_package (self-sign for user-supplied wallets). The resource and action are unambiguous.

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?

The description explicitly names alternatives and when they apply: data_preview for a free first taste, and data_session_funding_package for user-supplied wallets that must self-sign. It also states hard constraints: testnet only, requires an agent API key, not guest-callable. This gives an agent clear routing guidance beyond the tool name.

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