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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description contributes genuine context beyond them — the tool's role as a pre-flight check to prevent redundant on-chain approvals — though it says nothing about latency, batching, or behavior for unknown token addresses.

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, zero waste: the capability first, then the workflow rule. Nothing is buried or repeated from the structured fields.

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?

Annotations carry the safety profile, the schema fully documents all four parameters including chain options, and an output schema exists so return values need no explanation. Everything an agent needs to call this correctly is present.

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% and each parameter already documents itself (chain IDs, owner vs spender, token list). The description only restates 'spender address' and adds no format, batching, or validation semantics, so it sits at the baseline.

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+resource: 'Check ERC20 token allowances for a spender address', scoped to a particular owner/spender/token triple. It distinguishes itself from read_wallet_balances (balances) and write_wallet_approve (mutation) without requiring a schema read.

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?

Explicitly names the sibling it precedes (write_wallet_approve) and states the decision rule: skip approving if the current allowance is already sufficient. This is a clear when-to-use plus a concrete branch condition, leaving little to inference.

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