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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description goes beyond by specifying the transformation behavior: only A-Z letters are changed, others remain, and decoding reverses the shift. It does not explicitly address case preservation, but it does not contradict annotations. This adds meaningful behavioral context beyond the structured hints.

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 three sentences with no wasted words. The core purpose is front-loaded, followed by the key mechanics and a source link. It is efficiently structured and each sentence 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?

For a simple transformation tool with a rich input schema and an output schema (per context signals), the description covers everything an agent needs to call it correctly: what it does, how the shift works, and edge cases like non-letters. There is no missing information that would prevent 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 description coverage is 100%, so all three parameters (text, shift, mode) are documented. The description reinforces the shift meaning by noting that 13 equals ROT13, which adds a useful reference. However, it does not add new semantics beyond what the schema already conveys; the baseline of 3 is appropriate because the schema handles the heavy lifting.

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 precise verb and resource: 'Encode or decode text with a Caesar shift cipher.' It immediately clarifies the operation (encode/decode) and the specific cipher type. The mention of ROT13 as shift 13 differentiates it from sibling ciphers like hopi_vigenere_cipher, and the explanation of only A-Z letters being altered gives a concrete scope.

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 clearly states what the tool does and the mechanics (shift amount, ROT13 equivalence, non-letter handling). It does not explicitly name alternatives or conditions when not to use it, but given the self-evident name and the context of a simple utility, the intended usage is clear. No exclusions are mentioned, but the description is adequate for typical usage.

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