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

Annotations provide only generic hints (not read-only, not idempotent, not destructive, open-world), so the description carries the behavioral burden. It discloses routing/failover/cache/metering behavior, return shapes for success and refusal (including request_id and doorway in error.data), unit metering rates, and API-key requirement. This goes well beyond annotation coverage.

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 dense and front-loaded with the core action, then moves into usage guidance, exclusions, return format, and metering. Every sentence contributes; the only mild overhead is the reference to 'the same routing, failover, cache and meter as POST /rpc/{chain}', which assumes endpoint familiarity but still adds context.

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 low-level RPC passthrough with no output schema, the description covers inputs, return values, error behavior, billing impact, authentication need, and routing decisions among sibling tools. An agent can select and invoke this tool correctly without external documentation.

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?

Schema coverage is 100%, but schema descriptions are terse ('Chain slug', 'JSON-RPC method'). The description adds the actual allowed chain values for `chain`, examples like 'eth_blockNumber' and 'eth_getBalance', and clarifies that `params` follows the method's expectations. This materially improves a caller's ability to supply valid arguments.

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 ('Send one JSON-RPC call') and a precise resource (the FlexYield gateway), then gives chain values, method examples, and the exact role of params. It also differentiates itself from shaped sibling tools by covering reads that they do not.

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?

Use conditions are explicit: 'for any read the shaped tools do not cover' and 'for sending signed transactions.' Exclusions name specific siblings — get_balances, get_history, get_tx_status, get_quote — and the reason (shaped tools offer one call, decoded). This leaves little to inference.

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