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

With no annotations, the description carries the full burden. It discloses payment requirements, the call URL and header, and a limitation (no stress_level categorical). It implies read-only behavior by stating 'evidence only' and 'Returns', but does not explicitly declare safety or describe error handling or rate limits.

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 a single, information-dense paragraph covering payment, components, output, limitation, and access URL. All sentences are relevant, though the emoji and 'New wallets get 5 free units' add minor fluff. It is well-structured and front-loaded with the most critical payment requirement.

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?

There is no output schema, so the description explains the return fields (reason_codes, signal_strength, risk_band) and the data sources. It also covers the notable absence of the stress_level field. While it does not detail the meaning of the return fields, the description is reasonably complete for a no-input evidence tool.

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?

The tool has zero parameters, so the schema is already complete. The description does not need to explain inputs, and it doesn't introduce any parameter-related ambiguity. The baseline of 4 is appropriate as no compensation is needed.

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 clearly states the tool provides a 'US financial stress composite' composed of VIX, HY spread, TED spread, and STLFSI, and explicitly lists the output fields (reason_codes, signal_strength, risk_band). It distinguishes itself from siblings by emphasizing 'evidence only' and noting the absence of the 'stress_level categorical' field.

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?

It provides clear contextual guidance by stating it is a premium tool requiring x402 payment, and notes this is 'evidence only' with no categorical stress level, indicating when not to rely on it for categorical outputs. However, it does not explicitly name alternative sibling tools for similar purposes.

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