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

Beyond the readOnlyHint/openWorldHint annotations, it discloses genuinely useful behavior: the validate-and-retry-with-errors loop, the guarantee of schema-valid output or the exact residual errors, the 16,000-character input cap, and the $0.025 USDC x402 cost per call. Cost and input limits are exactly the kind of context annotations cannot carry.

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?

Three tight sentences, front-loaded with the core capability, then behavior guarantee, then limits and price. No filler or redundancy; each sentence adds a distinct fact.

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?

With no output schema, the description does explain the return contract (valid JSON or the exact errors), which is good. But for a three-parameter tool with a nested schema object and zero schema documentation, leaving 'instructions' unexplained and omitting failure/cost semantics on retry leaves meaningful gaps.

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 0%, so the description carries the full burden. It lightly characterizes 'text' (any text, up to 16,000 chars) and 'schema' (YOUR JSON Schema), but the third parameter, 'instructions', is never mentioned, and there is no guidance on schema format or how instructions shape extraction.

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?

States a specific verb and resource: turn text into JSON conforming to a caller-supplied JSON Schema, with the extraction/validate/retry pipeline made explicit. This is far more concrete than the title 'structure'. However, it never distinguishes itself from nearby siblings such as extract, json_validate, or json_repair, so an agent must infer which one to pick.

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 explains the mechanism but gives no when-to-use guidance, no prerequisites, and no named alternatives. With siblings like extract and json_validate in the same namespace, the absence of any routing statement leaves selection ambiguous.

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