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

Goes well beyond the annotations: it discloses error semantics (422 not charged, 5xx not charged and why), expected latency, price, a shared free-tier quota, and an explicit untrusted-data warning. Annotations already cover safety (readOnly, idempotent, non-destructive); the description adds the operational and trust posture an agent needs.

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?

Dense but front-loaded: purpose first, then inputs, returns, error behavior, timing, and pricing. Every clause carries information, though the pricing/free-tier detail makes it heavier than a purely discovery-oriented description needs to be.

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 enumerates the return fields (allowance_raw, allowance, decimals, symbol, unlimited) with the 2^255 threshold, and covers error, latency, and cost dimensions needed to call the tool 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 description coverage is 100%, so the four parameters are already documented in the schema, including the chain enum and the 0x+40-hex patterns the description repeats. The description adds no syntax or format meaning beyond the schema, so the baseline of 3 is appropriate.

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 (read an ERC-20 allowance) and scopes it to two named chains. An agent can distinguish this from siblings like get_balance or get_token_info without opening a 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 gives clear context for when the tool applies (reading approval state on Ethereum or Base) and adds operational conditions (422 for non-readable ERC-20, 5xx for bad node data). It does not explicitly route the agent away from or toward sibling tools such as check_contract_before_interaction or get_token_info, so a 4 rather than 5.

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