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

With no annotations, the description carries the full behavioral burden, and it does disclose one important non-obvious trait: the $0.001 USDC charge on Base via x402. It still omits determinism, output encoding/format, and any key-length or secret-handling caveats, so a mutation-adjacent crypto tool remains partially opaque.

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 compact sentences, front-loaded with the action and followed by the cost note; no filler. Slightly dense with use-case keywords, but every clause is relevant.

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?

For a 3-parameter tool with no annotations and no output schema, the description covers purpose and cost but leaves the return format (hex digest? base64?) and the optional-algorithm default unspecified, which are the main gaps an agent needs closed before calling.

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 0%, so the description must compensate. It names the algorithm choices (SHA-256/SHA-512, already in the schema enum) and the HMAC concept implies a text and key input, but it never states what an omitted algorithm defaults to, nor clarifies the secret 'key' semantics or size limits.

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+resource ('Compute an HMAC for text') plus the supported algorithms and typical applications, so an agent knows what operation is performed. It does not, however, differentiate itself from close siblings like hash or multi-digest-checksum, which an agent must disambiguate on its own.

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 named scenarios ('signatures, webhook verification and agent integrity checks') imply when this tool is appropriate, which is better than nothing. There is no when-not guidance and no explicit routing against the sibling hash/multi-digest-checksum tools that look similar.

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