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

Goes well beyond the readOnlyHint/openWorldHint annotations: it discloses the pricing model ($0.002 USDC per successful call), the payment rail (x402 on Base/Solana/Arc), that failed calls are not charged, and that output is model-dependent JSON. Cost and billing behavior are exactly the traits annotations cannot convey.

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?

Front-loaded with the core operation and constraints before the model/pricing details, and every sentence carries weight (limits, modes, cost). Slightly dense with the parenthetical payment rails, but nothing is wasteful.

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 4-param, required-labels tool with an output schema present, the description covers the operation, input limits, output shape (confidence, reason), model dependency, and full cost/payment terms. An agent has everything needed to invoke and price the call.

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 coverage is 100%, so baseline is 3, but the description adds real meaning beyond the schema: it clarifies the exclusive-vs-multi label mode ('one label per text, or several with multi true') and that each text returns a confidence 0-1 plus a one-line reason. It does not explain text vs texts redundancy, keeping it just above baseline.

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+resource ('labels up to 20 texts') with concrete operating constraints (2-20 labels you choose, one or several per text). The mechanism of user-supplied labels implicitly distinguishes it from fixed-scheme siblings like sentiment or moderate, so an agent can tell what this does without opening the schema.

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?

Usage is implied by the operational detail (you supply the labels; use multi for several per text), but there is no explicit when-to-use vs alternatives, no mention of sentiment/moderate/text_keywords as siblings to route around, and no preconditions. Adequate but leaves routing to inference.

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