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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so safety is covered. The description adds genuinely new context beyond them: the index itself is free and keyless, while the underlying full texts are gated and sold per-read via x402, which materially affects how an agent should treat the returned entries.

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, resource-first, with the payment/auth caveat trailing. The middle field enumeration (question, verdict, evidence class, data window, per-read price, address) is dense but each item earns its place by describing the payload.

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 has to carry the return shape — and it does by listing the fields each study entry exposes. Combined with annotations covering safety, the definition is essentially complete for a parameterless listing 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?

With zero parameters there is nothing for the description to disambiguate, so the baseline for a 0-param tool applies. The description appropriately spends its words on the returned content instead.

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?

It identifies a specific resource (the Coil Edge Research index) and enumerates what each entry contains, so an agent can tell it apart from the market/crypto/cart siblings. The verb is only implied by 'index' rather than stated, but 'every published backtest study' makes the listing behavior unambiguous.

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 only implied: 'Free and keyless' tells the agent it can call this without auth, and the note that studies are sold one read at a time over x402 hints at the browse-then-pay flow. It never explicitly states when to reach for this versus the board/read siblings, so the guidance stays implicit.

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