try_keys

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

With no annotations, the description carries the full burden and does well: it discloses both cipher modes tried, the zero-IV assumption, output ordering, where plaintext samples appear, how scoring behaves, and that malformed key lengths (not 16/24/32) or payloads (not a multiple of 16) are silently skipped. Missing only runtime/cost expectations for large key × payload cross products.

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 action and mode coverage, then caveats, then validation rules. Three tight blocks with no filler. The scoring paragraph could be one clause shorter but every sentence carries information an agent needs.

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 pure-compute crypto tool with an output schema covering return values, the description supplies the mode set, ordering, caveats, and skip rules — everything needed to call it correctly and interpret the score. Only performance expectations are absent, which is minor.

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 0%, so the description must compensate, and it does: keys_hex implicitly requires 16/24/32-byte values and payloads_hex requires hex blocks that are multiples of 16 bytes. The 'samples holds the first plaintexts as hex' line clarifies the output shape even though an output schema exists. It doesn't state that both parameters are arrays or their ordering/cardinality relationship.

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: decrypt hex payloads with each candidate AES key, in ECB and CBC with a zero IV, returning best-scoring first. An agent knows exactly what the tool computes. It doesn't explicitly contrast with siblings (guess_checks is the nearest), but no sibling actually overlaps this operation.

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?

Usage is implied rather than stated: use it when you hold candidate keys and captured payloads. The note that scores only discriminate across several distinct payloads (and that one payload makes every key score 1.0) is effectively a when-not-to-use warning. No alternative tool is named for any case.

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