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

With no annotations, the description fully discloses behavior: snapshot-based (refreshed from FxAI scan engine), informational only, output details (zone, score), payment model ($0.01 per call, trial, x402 on X Layer), and that the first paid call opens a 6-day trial. No side effects or destructive actions implied.

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 relatively long but each sentence adds essential information (pair details, output, snapshot, payment, comparison to sibling). It is front-loaded with the core verdict and pair scope, making it efficient despite verbosity. Minor redundancy could be trimmed, but overall well-structured.

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 one parameter, no output schema, and no annotations, the description provides a comprehensive picture: it explains the output format (zone, score), data freshness (snapshot), payment model (cost, trial, payment method), and how to proceed with payment (402 header). It also references the sibling 'pitch' tool for a free alternative, leaving no obvious gaps.

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 single parameter 'symbol' has a schema description, but the description adds valuable context: acceptable forms (EUR, EURUSD, EURUSD=X), the scope of 47 pairs (24 vs USD, 23 vs KRW), and that it accepts shorthands. This goes beyond the schema's basic type and description.

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 it returns a bottom/top verdict for one currency pair, lists the 47 pairs in the snapshot, explains acceptable symbol formats, and describes the output fields (zone, score). It distinguishes itself from the sibling 'pitch' tool by covering any symbol and providing a per-indicator breakdown.

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?

The description explicitly contrasts this tool with the free 'pitch' tool, noting that 'pitch' only shows a live verdict for the showcase symbol while this tool answers any symbol and adds the breakdown. It also includes payment prerequisites and how to handle the 402 challenge, providing clear when-to-use and alternatives.

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