Safelisted read-only multi-chain JSON-RPC call

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

Annotations already provide readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context beyond these hints: the exact cost ($0.003 per call) and the explicit statement that write methods are never permitted. This aligns with the annotations and gives the agent crucial operational details.

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 extremely concise (two sentences) yet packs all key information: purpose, supported chains, example methods, constraint against writes, and cost. It is front-loaded with the core purpose and flows logically. Every sentence earns its place with no filler.

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 tool's complexity (multi-chain RPC proxy), the description provides essential information: supported chains, allowed methods, cost, and safety. There is no output schema, but as a proxy the return value is the standard JSON-RPC result, which is implicit. Minor improvements could include note on rate limits or authentication, but the description is largely complete for decision-making.

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% with parameter descriptions for chain, method, and params. The description adds value by stating defaults ('default base' for chain, 'default []' for params) and providing concrete examples like 'eth_call, eth_getBalance' for the method parameter. This enhances the schema information, though the schema descriptions were already adequate.

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 tool as a safelisted read-only JSON-RPC proxy across multiple chains (Base, Ethereum, Polygon, Arbitrum, Optimism) and lists specific supported methods like eth_call and eth_getBalance. This distinguishes it effectively from sibling tools that cover more specific blockchain queries (e.g., get_wallet_balance, get_gas_price).

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 states that write methods are never permitted, which tells the agent when not to use the tool. However, it does not explicitly compare this tool to its siblings or provide guidance on when to prefer it over more specialized tools like get_crypto_price or get_wallet_balance. The agent is left to infer that this tool is for arbitrary RPC calls not covered elsewhere.

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