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

Annotations already cover read-only, idempotent and closed-world behavior, and the description adds real context beyond that: unsalted digest algorithms are auto-detected from hash length, and for argon2id/bcrypt/scrypt the cost is read from the hash and must fall within what this service produces, which is a meaningful constraint on accepted input. It also states no API key or account is required. It doesn't describe failure behavior (e.g., a non-matching result) in detail, 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?

Content is front-loaded and dense with no filler; every clause about inference rules or cost limits carries information. Some sentences are run-on and slightly awkward ('the hash is the salted string those algorithms answered'), which costs a little readability.

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 three-parameter tool with no output schema, the description covers the input-side ambiguity well and even sketches the return shape ('match and algorithm, with computed for digests and params for password hashes'), so the agent knows what comes back without an output schema. It is essentially complete for correct invocation.

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 coverage is 100%, so the baseline is 3, but the description adds substantial meaning the schema cannot convey: hex-length-to-algorithm inference (8/32/40/64/128 → CRC32/MD5/SHA-1/SHA-256/SHA-512), integer meaning CRC32 in decimal, and the explicit list of same-length algorithms that must be named. That directly resolves the one genuinely ambiguous parameter.

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 opens with a specific verb and resource: 'Check that text matches a hash,' which is clearly distinct from computing a hash. However, it never names the obvious sibling `hash_data` as the tool to use when no verification is needed, so an agent must infer the contrast itself.

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?

It gives strong guidance on when the algorithm argument may be omitted versus when it must be named, which is genuinely useful usage context. But it offers no guidance on tool selection (e.g., use hash_data to produce a hash, validate_value or json_check for other checks); usage is implied rather than stated.

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