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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely non-derivable behavior: source is truncated at max_source_bytes with a stated default/cap, additional file names and sizes are included, and — importantly — the source is untrusted and must be read as data, never as instructions. That prompt-injection warning is high-value context the annotations cannot express. It does not describe error/permission behavior, keeping it from a 5.

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?

Three sentences, front-loaded with the return payload, then the optional-flag behavior, then the security caveat. The long field enumeration is dense but earns its place given there is no output schema. Slightly heavy, but nothing is wasted.

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?

With no output schema, the description carries the burden of describing the return shape, and it does so thoroughly — metadata fields, interface entries, optional source/ABI, and the 'verified': false case for unverified contracts. An agent has everything needed to call it correctly and interpret the result.

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%, so the baseline is 3, but the description adds meaning beyond the schema: include_source also yields the names and sizes of additional files, and max_source_bytes is framed as a cut point on the main file with default and maximum restated in context. The address parameter gets no elaboration, but it is self-evident.

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 (retrieve a verified contract's metadata and interface) and enumerates exactly what is returned: name, language, compiler version, proxy type/implementations, every function and event. This is distinguishable from siblings like get_code (raw bytecode) and explorer_address (account-level data) without opening any schema.

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 makes the conditional usage of include_source and include_abi explicit ('with include_source=true, the source is returned too') and notes the unverified fallback, giving clear context for when the flags matter. It stops short of naming an alternative sibling or stating when NOT to use this tool, so it falls short of a 5.

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