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

With no annotations, the description carries the behavioral burden. It discloses the cost, the endpoint URL, and the important behavior that unauthorized calls return a payment requirement rather than data. It does not cover rate limits or exact response structure, but the core invocation behavior is transparent.

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?

Two sentences with no filler. The price and endpoint are front-loaded, followed by the functional purpose and the payment/authorization behavior. Every clause contributes necessary information.

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?

The definition is solid for a paid read-only API, but gaps remain: no exact response fields, no error/payment-requirement response shape, and no guidance on how the `payment` header maps to the `payment` schema property. Given no annotations and no output schema, a bit more detail would be needed for fully reliable invocation.

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 0%, so the description must explain the three parameters. It maps api_key, payment, and bundle_token to distinct authorization paths ('free-tier api_key', 'payment header', 'prepaid bundle_token') and says how to obtain an api_key. It could clarify formats or whether 'payment header' means the `payment` parameter, but it adds meaningful semantics beyond the bare schema.

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?

Description states a specific resource ('market breadth') and concrete output components: top-50 breadth, BTC dominance, XLM relative strength, and a single risk-on/risk-off verdict. This clearly distinguishes it from siblings like get_fear_greed_index or get_prediction_market_pulse.

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?

Provides clear context: it is a market regime check and it is paid ($0.10/call). It tells the agent that calls require a payment header, bundle_token, or free-tier api_key炴and directs to get_free_api_key for minting one. It does not enumerate functional alternatives, but the context is clear.

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