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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds valuable context beyond those: the tool is paid ($0.001 USDC on Base or Solana) and returns a hex digest. It does not contradict the annotations. The only shortfall is ambiguity about how the payment is handled, but the key cost trait is disclosed.

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 extremely concise with no filler, fitting the algorithm, output format, and cost into a short sentence. The structure is somewhat awkward because it opens with the pricing detail rather than a verb/object construction, but it remains efficient.

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 simple two-parameter cryptographic function, the description conveys the algorithm, output, and cost. However, it leaves operational questions unanswered: how the $0.001 payment is made, what 'on Base or Solana' means for the caller, and whether the input/secret are UTF-8 strings. With no output schema and no parameter descriptions, these gaps are meaningful.

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 schema has 0% description coverage, and the description does not explicitly map `input` and `secret` to message and key. However, the HMAC-SHA256 context strongly implies that `input` is the data and `secret` is the key, adding some meaning beyond the bare schema. Explicit encoding or format details are still missing.

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 names the exact algorithm and output format ('HMAC-SHA256 hex digest'), which clearly distinguishes it from sibling hashing tools like sha256 and keccak256. However, it lacks an explicit verb (e.g., 'computes') and reads as a fragment rather than a full statement of what the tool does.

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 provides no guidance on when to use this tool versus alternatives such as sha256 or sha512, and no exclusions are stated. The HMAC-SHA256 label implies usage for authenticated digests with a secret, but the description does not explicitly say when this tool should be chosen over a plain hash.

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