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

Annotations already cover read-only and idempotent, so the lower bar applies; the description still adds the return shape (JSON { match: boolean }) and an error-path hint about the accepted bcrypt prefixes ($2a$, $2b$, $2y$). It does not mention cost-factor or timing concerns, but the added context is concrete and useful.

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 with the purpose, then return value, example, and error note in four compact lines. The example input is slightly verbose but short enough to earn its place as a format guide.

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?

No output schema exists, and the description fills that gap by declaring the return object; it also pre-empts the most likely failure mode (malformed hash) with the accepted prefix list. For a two-parameter pure function this is complete.

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 baseline is 3; the description goes further by giving a concrete example payload and by constraining the hash parameter to full bcrypt strings with the accepted prefix set. That is real added meaning beyond the schema's terse 'Bcrypt hash to verify against.'

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 ('Check whether a password matches a bcrypt hash'), which is unambiguous and clearly distinct in meaning from bcrypt_hash. However, it never names the sibling that produces the hash or hash_compare, so the differentiation is implicit rather than explicit.

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?

The verification use case is obvious from the description, but there is no statement of when to prefer this over bcrypt_hash (to create) or hash_compare (other algorithms), and no prerequisite notes. Usage is implied only.

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