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

Beyond the annotations, the description discloses the paid nature (300 micro-dollar credits per successful call), the dependency on agent_utilities_prepare, the authentication requirement, and important idempotency/recovery semantics (reusing requestId, new requestId is a new billable operation). This goes well beyond what the schema or annotations provide. No contradiction with annotations is present.

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 sentences, each earning its place: function, cost, prerequisite/auth, and recovery semantics. The most important information is front-loaded, and there is no filler or redundant restatement of the schema.

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 paid tool with a prerequisite and recovery semantics, the description covers all operational essentials: what it does, how to prepare, what access is needed, what it costs, and how to avoid double billing. An output schema exists, so return-value details do not need to be in the description.

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 67%, with requestId and maxPriceMicroUsd already described in the schema. The description adds meaningful semantics for the paths parameter by identifying them as RFC 6901 pointer strings and reinforcing the 100-pointer limit. The input.data parameter remains generic, but the phrasing 'Select JSON values' implies it is the JSON document to traverse, so the description sufficiently compensates.

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 verb ('Select') and resource ('JSON values') using RFC 6901 pointer strings, and clearly distinguishes the tool from siblings like data_json_diff, data_json_patch, and data_json_canonical. It also adds a meaningful behavioral nuance: preserving missing versus null.

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 clear operational context: use agent_utilities_prepare first, existing credits and a private Authorization header are required, and prepared arguments should be reused for recovery. It does not explicitly mention alternatives or when-not-to-use scenarios, but the prerequisite and recovery guidance is strong enough for an agent to invoke this correctly.

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