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

Annotations already declare readOnly, openWorld, non-idempotent, non-destructive. The description adds real value beyond that: the payment/auth requirement, the exact failure mode (PaymentRequired object), the evaluation cadence (every calendar day incl. weekends), and the stamped close used. This is meaningful behavioral context.

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 what the signal is and how it is computed, then the access/payment terms. Dense but each clause carries information; slightly long but no filler sentences.

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 carries the return-value burden and does reasonably well, naming the output values (LONG or CASH per sleeve) and the error case. An agent has enough to call it and interpret the result, though exact response shape is only sketched.

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?

Zero parameters, so there is nothing to document and the baseline of 4 applies. The description correctly implies no input is required.

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 (crypto trend signal) and enumerates the mechanics (LONG/CASH per sleeve, 50-day gates, BTC 200-day master gate). It also signals the differentiator from the free tier ('one close ahead of the free tier'), though it never names get_crypto_trend as the alternative, so differentiation is implied rather than explicit.

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?

Clearly states the access conditions: a Coil Live subscription or an x402 wallet, and the consequence (PaymentRequired object, no data) otherwise. It does not, however, tell the agent when to choose this over the free get_crypto_trend sibling beyond the implicit 'one close ahead' hint.

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