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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds genuinely new behavior: determinism, the 100 KB input cap, UTF-8 encoding, and the returned string format. Only pagination/error behavior is absent, which is minor for a pure function.

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?

Four short sentences, each load-bearing: contract, determinism, algorithm caveat, size limit. Output format and limit are front-loaded rather than buried.

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?

There is no output schema, and the description compensates by describing the return string explicitly. Combined with the size limit, determinism note, and annotation-backed safety profile, an agent has everything needed to call it correctly.

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?

With 100% schema coverage the baseline is 3, but the description adds UTF-8 encoding semantics and security-level framing for the algorithm parameter that the schema does not carry. The 'spaces and line breaks change the result' nuance is left to the schema.

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 and resource ('Hash text') plus the exact output shape ('sha256: ba78...' lowercase hex), which immediately separates it from encoding siblings like base64. An agent can tell what it produces without opening the 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?

Gives real selection guidance at the algorithm level ('MD5 and SHA-1 are only for checksums, not security; do not use plain hashes to store passwords'), which steers the enum choice. It does not explicitly contrast with siblings like base64 or generate_password, so it stops short of full when/when-not routing.

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