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

With no annotations, the description carries the full burden and does disclose useful traits: it is a GET request, it is paid ('PAID inbound $0.01 → then proxy $0.0110'), and it proxies the pending block via eth_getBlockByNumber. However, it omits response format, error behavior, rate limits, and whether the network parameter is required or restricted.

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 compact and labeled: payment info, semantics, underlying method, upstream URL, method, and example query. The leading bracket notation is somewhat cryptic but not verbose, and the key information is front-loaded.

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?

For a simple GET proxy, the description covers the essential mechanics: URL, HTTP method, example query, and the meaning of 'pending'. However, there is no output schema and no description of the response shape, and the full set of accepted query parameters is not specified, leaving an agent to infer some behavior.

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 describes only generic 'body' and 'query' objects, so the description adds meaningful specificity with Method: GET and the example query {"network":"ethereum"}. This tells the agent a concrete query parameter name and value beyond the schema. It still leaves other possible query parameters undocumented.

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 names a specific resource and behavior: 'Pending block - transactions not yet mined' and ties it to eth_getBlockByNumber("pending"). This distinguishes it from sibling chain tools like block_number or tx_hash. It loses a point because it is a sentence fragment prefixed by ambiguous payment notation, rather than a clear declarative statement.

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 gives invocation details (Method: GET, upstream URL, example query) but does not state when to use this tool versus sibling onesource chain tools, nor does it provide exclusions or decision rules. 'Pending block' implies usage for unmined transactions, but that guidance is implicit rather than explicit.

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