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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful non-annotated behavior: 422 on non-ERC-20 addresses with no charge, failed calls free, per-call pricing, and the first-25-free allowance, which explains the non-idempotentHint. However, 'Reads or computes only and changes nothing' largely restates the annotations, and repeated free/charged phrasing dilutes the signal.

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?

Front-loaded with purpose and the key alternative, and the example is well placed. It is somewhat dense with pricing/credits details repeated in several forms ('uncharged', 'first 25 free', 'failed calls free', 'each call is charged'), which adds minor redundancy.

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 correctly compensates by naming the four returned fields. It also covers input formats, the error case, and cost model, leaving no obvious gap for an agent to call it correctly.

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. The description adds real value beyond the schema: it clarifies a ticker OR a 0x address is acceptable, gives a worked address example, and documents the failure mode (422, uncharged) for addresses that are not ERC-20 contracts.

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?

Specific verb ('look up') plus resource (ERC-20 token contract metadata on Mantle) and an explicit enumeration of the returned fields (name, symbol, decimals, total supply). It also distinguishes itself from mantle_token_balance by naming that sibling directly.

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?

States two concrete use cases ('identify an unknown token address', 'format raw amounts') and an explicit when-not with the alternative tool ('for a holder's balance use mantle_token_balance'). Nothing is left to inference.

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