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

The annotations already declare readOnlyHint=true and openWorldHint=false, and the description reinforces this by stating that nothing executes and no API call is made, which is genuine added context about side effects. It also discloses the class of errors caught (unknown fields, grammar violations), which goes beyond the annotations. The one gap is that it never indicates what a failure result looks like, and there is no output schema to cover that.

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?

Three sentences, front-loaded with the action and the timing constraint, with zero filler. The parenthetical example about getDigits.action is long but genuinely instructive, so it earns its space rather than being padding.

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 two-parameter, non-executing validation utility, the description covers inputs, validation behavior, cost, and side effects. The only missing piece is response shape (a pass/fail flag versus a list of errors), which matters more here because no output schema exists, keeping this short of a 5.

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 would be 3, but the description adds real meaning by explaining that the json/xml choice changes the validation regime: schema conformance for JSON versus well-formedness plus element/attribute grammar for XML. That helps an agent reason about format selection beyond the schema's 'json or xml; auto-detected' note.

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 uses a specific verb-plus-resource formulation ('Validate a Sautikit voice-actions document') and immediately clarifies the point in the workflow ('BEFORE wiring it to a number'). The sibling tools (list_webhooks, list_webhook_deliveries) are unrelated to validation, so no disambiguation is needed, and an agent can identify this tool's job from the first clause alone.

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 a clear usage context: run this before wiring the document to a number. The cost framing ('Local and free: no API call, nothing executes') further signals that this is a cheap pre-check to run liberally. It stops short of naming explicit alternatives or when-not-to-use cases, but the workflow positioning is unambiguous.

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