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

With no annotations, the description carries full burden. It proactively discloses payment requirements (signal credit or x402 USDC), cost range, authentication needs (X-API-KEY), and the 402 payment envelope for uncredentialed calls. This goes beyond typical read-only tools and covers critical operational behavior, though it does not detail the response format.

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 dense single sentence but efficiently packs essential details: strategy, scope, payment, auth, and endpoint. It is front-loaded with 'Coin Flipper' and immediately clarifies the actual function. While verbose, every segment serves a purpose, though it could be restructured for readability.

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?

Given no output schema, the description should clarify what the tool returns. It describes the scan inputs and methodology but omits what the response contains (e.g., list of signals, prices, probabilities). It also relies on 'instruments' for parameter docs, shifting documentation burden. The payment and authentication details are covered, but the output contract is vague, making the description incomplete for a complex paid signal 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 schema has zero defined properties, but the description explicitly mentions a 'class' parameter with values 'fx|equity', adding meaning beyond the empty schema. It also directs users to the 'instruments' tool for endpoint parameter docs, which supplements the schema. For a 0-parameter baseline of 4, the added class guidance justifies a 5.

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 states a specific verb+resource: 'Coin Flipper' scanning Polymarket daily Up/Down across FX pairs and equities, with a distinct methodology (fair-value band vs venue book, interval-disjoint divergence). This clearly distinguishes it from sibling tools like signal_equities or scan_forex by naming the strategy and scope.

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 provides clear context for when to use the tool (daily Up/Down signals on FX/equities) and even mentions a filter (?class=fx|equity) to narrow scope. It does not explicitly exclude alternatives, but the specific coverage and strategy imply its niche, making usage context clear without an explicit when-not list.

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