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

Annotations already declare readOnlyHint and openWorldHint, so safety and network scope are covered. The description adds genuinely useful context beyond annotations: the no-API-key requirement and the x402 USDC per-call cost. However it omits rate limits, error behavior, and what 'read access' excludes, so it adds some but not rich behavioral context.

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?

Two sentences, front-loaded with the core purpose (JSON-RPC read access + chain list), then the call format and cost. No wasted words. Slightly dense but every clause carries information.

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 5-parameter passthrough tool with no output schema and only 20% schema coverage, the description covers chain scope, method examples, auth (no key), and cost. But it leaves parameters like params/jsonrpc/id unexplained and doesn't state response shape or failure modes, leaving notable gaps for a tool whose input schema is largely bare.

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 description coverage is only 20%: chain has an enum-like description but id, method, params, and jsonrpc are undocumented. The description partially compensates by naming example methods (eth_call, eth_getBalance, etc.), which clarifies the method parameter's expected values, but does not explain params reshaping, jsonrpc version, or id semantics. Baseline is below 3 for low coverage, lifted by the method examples.

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?

States a specific verb+resource: JSON-RPC read access to named EVM chains, with example methods. An agent can tell this is a raw JSON-RPC passthrough for EVM chains. It does not explicitly distinguish itself from siblings like contract_inspect, tx_decode_raw, or wallet_portfolio, which partially overlap in EVM read functionality.

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 implies when it's useful by listing example JSON-RPC methods, and 'read access' scopes it to reads. But it gives no explicit when-to-use vs alternatives guidance: an agent cannot tell whether to prefer this over contract_inspect, tx_simulate, or wallet for a given read task. Adequate minimum viable context, no routing.

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