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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered; the description nonetheless restates no-network/no-state and adds hard limits (64 KB JSON input, 1 s per call, 1 MB result) that the annotations do not carry. The determinism statement is largely redundant with idempotentHint, which keeps it from a 5.

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?

Front-loaded and well structured with When / Not for / Side effects / Deterministic / Limits headings, but the entire content is delivered twice (Spanish then English), roughly doubling length with no new information. Each language version individually earns its place; the duplication does not.

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?

Output schema exists, so return values need no explanation, and the description covers what remains: what the tool computes, when to use it, the legacy-hash caveat, determinism, and explicit size/time limits. Nothing an agent needs to invoke it correctly 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?

Schema description coverage is 100% and every parameter has a description, enum and default, so the schema does the heavy lifting. The description only echoes that data and key may be text, hex or base64; it adds no interpretation of key_encoding vs. input_encoding confusion or output_encoding choice. Baseline 3 applies.

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?

Specific verb + resource ('Computes the HMAC (RFC 2104) using MD5') with the supported data/key/output encodings named, plus an explicit RFC reference. The agent can distinguish it from hmac-sha256, hmac-sha1 and hash-md5 without opening any 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?

Explicit 'When' (signing or checking a message with a shared secret passed in the call) and 'Not for' (hmac-sha256) clauses, plus a note that MD5 is legacy and SHA-256 is the modern default. The gap: the sibling list contains hmac-verify, and the description's 'or a signature checked' arguably points at that tool without naming it, so the routing between compute-and-compare vs. verify stays slightly ambiguous.

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