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

Annotations already cover readOnly, idempotent, openWorld and non-destructive, so the description is not burdened with the safety profile. It adds real context beyond that: results are decoded, a historical block is optional, and there is a 10 calls/day free tier with $0.001 per call afterwards via HTTP or X-API-Key credits. Rate-limit and cost disclosure is exactly the kind of behavior annotations cannot express.

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 dense clauses with the core capability front-loaded and the example signature immediately after. The pricing sentence is slightly crammed but it is genuinely actionable information rather than filler. No wasted framing.

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?

Five parameters, three required, all documented in-schema, and an output schema exists so return format need not be explained. The description covers capability, decoding, historical block support and cost model. Only the relationship to sibling read tools is unaddressed.

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% and every parameter carries its own description and example, so the schema does the heavy lifting. The description restates 'human signature and args' and flags the block as optional/historical, which is essentially duplication of what the schema already declares. Baseline 3 applies.

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 and resource: calling any view function via a human-readable signature with args, returning a decoded result. From this an agent knows exactly what the tool does. It does not, however, distinguish itself from nearby siblings such as contract_abi, token_balances, or calldata_decode, so it stops short of a 5.

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?

Usage is implied rather than stated: the mention of 'view function', 'human signature' and 'optional historical block' hints at when this fits. There is no explicit when-to-use, no when-not-to-use, and no routing toward siblings like token_balances for standard reads or contract_abi for building calldata.

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