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

With no annotations, the description carries the full burden of behavioral disclosure. It states the core behavior (encrypt/decrypt) and the 'offline' nature, which is useful. However, it does not explain the output format, how the 'd' flag affects behavior, or edge cases like non-alphabetic characters or case sensitivity. This is a moderate gap given the tool's simplicity.

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?

The description is a single, compact sentence that front-loads the purpose and includes the essential input format. There is no wasted wording, and it avoids redundancy with the schema. However, it might be slightly too terse, leaving out some behavioral details, but for conciseness it is effective.

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?

The tool is simple with one parameter and no annotations. The description covers the primary purpose and input format but omits the output structure and any error handling or edge-case behavior. Since an output schema is present but not detailed, the description should have described the return value. This is a moderate gap for a cipher tool, but given the simplicity, it is minimally adequate.

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?

The schema has a single undocumented parameter 'q' with 0% coverage, so the description must compensate. It does so by specifying the exact input format: 'KEY:text[:d]', which explains how the parameter should be structured. This adds significant meaning beyond the bare schema, making the parameter's purpose and syntax clear.

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 clearly identifies the tool as a Vigenere cipher for encryption/decryption and provides a concrete input format ('KEY:text[:d]'). It distinguishes itself from sibling cipher tools like caesar, atbash, and railfence by naming the specific algorithm, making its purpose unambiguous.

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 description gives no guidance on when to use this tool versus alternatives. It only mentions 'offline' as a constraint but does not explain when a user would prefer Vigenere over other ciphers, nor does it specify any exclusions or conditions. The usage context is left entirely to inference from the tool's name.

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