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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds meaningfully beyond that with 'Hashing happens here; nothing is stored,' clarifying that computation is local and no state is persisted — exactly the reassurance an agent needs before calling.

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 short sentences with zero filler; the algorithm and output destination are front-loaded and the no-storage guarantee follows immediately. Every clause earns its place.

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 value details need not be explained, and the description correctly points at the downstream consumer. For a one-parameter pure function this is nearly complete; only a note on expected input edge cases (empty string, encoding) would close the gap.

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 a single parameter at 100% schema coverage, the schema already explains 'Exact text to fingerprint (UTF-8).' The description's 'piece of text' adds no format, encoding, or edge-case detail beyond the schema, so 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?

Names the exact operation (SHA-256) and the resource (a piece of text), which an agent cannot infer from the name alone. The clause 'ready to pass to anchor_hashes' ties the output to a specific sibling, making it distinguishable from anchor_hashes and anchor_verify.

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?

'Ready to pass to anchor_hashes' establishes the intended workflow context: this is the local pre-step before anchoring. It gives clear positive guidance but no explicit exclusions or when-not-to-use conditions (e.g., hashing a file versus a string).

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