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

Goes well beyond the readOnly/destructive annotations: documents the error contract (404 for no contract, 422 for non-ERC-20, both uncharged), the billing model ($0.01/call via x402 or card key, first 25 free, failed calls free), and that repeats are not free. This is exactly the kind of context annotations cannot convey.

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 the core purpose and return shape, and every sentence carries distinct information (usage, input format, errors, pricing). It is dense rather than bloated, though the pricing sentence is lengthy and could be trimmed slightly.

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?

There is no output schema, but the description enumerates the returned fields (raw amount, decimals, symbol, human-readable amount), so an agent knows exactly what it will get, plus error and cost behavior. Nothing needed to call it correctly is missing.

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 baseline is 3, but the description adds constraints not in the schema: both inputs are 0x addresses of 40 hex characters, and the token argument accepts either a ticker or a contract address. That is meaningful disambiguation for invocation.

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?

Names a specific verb and resource ('ERC-20 token balance of a wallet on Mantle ... via balanceOf'), enumerates the return fields, and explicitly distinguishes itself from the sibling mantle_balance for the native coin.

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?

Gives an explicit use case ('check stablecoin or token holdings before a transfer or trade') and an explicit exclusion routing to another tool ('for the native coin use mantle_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.