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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds useful behavioral context: it costs $0.001 USDC per call, supports a specific set of chains, and is byte-identical to a documented GET endpoint, which goes beyond the annotation defaults.

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?

The description is front-loaded with its core purpose, then cost, chains, and REST equivalence. It is compact, though the byte-identical GET URL adds some redundant detail that could have been shortened.

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 annotations covering safety, an output schema covering return values, and a schema covering all parameters, the description provides the remaining essential context: why to use the tool, what it checks, what it costs, and where it works. Nothing critical 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?

The input schema already documents all three parameters with 100% coverage. The description adds a concrete URL example showing chain, token, and tokenId, which is helpful, but it does not add material semantic meaning beyond what the schema already provides.

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?

The description states a specific operation: checking ERC-1155 support via supportsInterface, contractURI, and an id probe. It clearly frames this as a pre-flight check before assuming a contract is a 721, distinguishing it from balance/URI siblings like chain_1155_balance and chain_1155_uri.

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 an explicit use case: 'the pre-flight before a client assumes a contract is a 721 and sends the wrong call.' It also lists supported chains and a per-call cost, giving context for when calling is appropriate, though it does not explicitly name alternatives or when not to use it.

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