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

Annotations already declare readOnlyHint and openWorldHint. The description adds the return behavior: 'Returns the hex-encoded return data', which goes beyond annotations and is useful for the agent. No contradiction with annotations.

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 action, then return data, then usage. No wasted words; every sentence adds value.

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 call tool with no output schema, the description adequately covers purpose and return format. It does not mention revert behavior, but given the annotations and schema richness, this is acceptable. Could mention decoding with siblings but not essential.

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 100%, so baseline is 3. The description does not add additional parameter semantics beyond the schema; it only mentions return data, which maps to the call data parameter but not the others.

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 states 'Execute a read-only smart contract call on Ethereum mainnet' which is a specific verb+resource+network. It distinguishes from siblings by specifying 'on Ethereum mainnet' and 'read-only', differentiating from mezo_call and multicall/decode variants.

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?

Provides clear usage context: 'Use this to read contract state without sending a transaction.' This tells when to use it, but does not explicitly mention alternatives or exclusions for batch calls or decoders.

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