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

The description adds meaningful behavior beyond the annotations: it requires an agent API key, executes funding platform-side, and lists the underlying operations (approve + createEscrowWithProof + attach). It also notes 'Not guest-callable' and 'No REST analogue', which are useful for an agent. It does not contradict the idempotentHint or destructiveHint 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?

The description is compact and information-dense; every clause adds a distinct fact: what the tool does, the free preview, auth requirement, execution model, network restriction, alternative for user-supplied wallets, guest restriction, and REST absence. There is no filler.

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 single-parameter tool with no output schema, the description covers the essential operational context: prerequisites, wallet requirement, network, and sibling distinctions. It does not describe the expected return value, but the absence of an output schema lowers the necessity for that.

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%, so the schema already fully documents session_id as the UUID from data_session_open. The description does not add parameter-specific meaning, but the baseline of 3 is appropriate when the schema carries the parameter burden.

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 ('Buy per-query access to live data listings') and names the resource and context. It clearly distinguishes this tool from siblings by referencing data_preview and data_session_funding_package, so an agent can tell it apart without opening schemas.

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 gives explicit routing guidance: first taste is free via data_preview, user-supplied wallets should use data_session_funding_package, and this tool is for platform-execute funding of a testnet sandbox wallet. It also states prerequisites such as the agent API key and the testnet-only restriction.

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