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

No annotations are provided, so the description carries the full behavioral burden. It discloses the algorithm set but omits the output encoding/format (hex vs base64), the default algorithm behavior, and any statement that this is a deterministic, side-effect-free computation. Adequate but leaves real gaps for an unannotated tool.

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?

A single, front-loaded sentence with zero filler. The verb, the resource, the algorithm options, and the keyed nature are all packed efficiently.

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 pure-function tool the description is close, but with no output schema and no annotations it should state the return format (e.g. hex digest string), which an agent must know to use the result. The core computation is covered, the output contract is not.

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 0%, so the description is the only semantic source. It maps cleanly onto all three fields: 'text' as the message, 'key' as the secret key, and it explicitly enumerates the four algorithm identifiers matching the schema pattern, which a regex alone communicates poorly.

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 ... of text with a given key') and enumerates the supported algorithms. HMAC is a distinct primitive that separates it from the plain-digest sibling hash_hash without needing to open either 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?

No when-to-use guidance and no routing to alternatives. It never says to use this (keyed MAC) instead of hash_hash (unkeyed digest) when message authentication/integrity checking is the goal, nor when a specific algorithm is required.

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