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

With no annotations provided, the description carries the full behavioral burden and does it well. It explicitly discloses the API key bearer-token requirement and the pay-per-call option (2 cents via Binance b402 or x402 on Base). It also discloses the window boundary behavior (default 24, max 720). Missing details like rate limits or error handling keep it from a 5.

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 structure is somewhat dense and not front-loaded: the first and longest sentence is about authentication and payment logistics, while the actual functional description only appears in the second sentence. The payment details are relevant, but they could be summarized more concisely. The core purpose sentence itself is tight and informative.

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 the output schema and the input schema, the description provides sufficient context for an agent: what is returned, how the parameters behave, and the required payment/auth flow. Minor gaps remain such as unclear exactly how the sampled series is omitted, but they are not blocking. The description is complete enough to decide to call and invoke correctly.

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 no parameter descriptions (0% coverage), but the description fully compensates. It explains that window is measured in hours, provides the default value, and the maximum. It also explains the chain behavior with 'Omit chain for all nine', which is not obvious from the schema alone. This is exactly the kind of semantics a tool description should add.

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 identifies the resource (open interest per chain) and enumerates the exact data components ('latest value, the value at the start of the window, change in percent, high and low inside the window and a sampled series'). The explicit verb is missing, but the noun phrase 'Open interest per chain' functions as a clear resource description. It is distinguishable from the sibling market-data tools, though it does not name any alternatives.

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 communicates how to use the parameters (window in hours, default 24, max 720, omit chain for all nine) and the required authentication/payment model. However, it provides no explicit guidance on when to use this tool versus related siblings such as candles or prices. The usage context is implied: if you need open interest data, use this tool.

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