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

Annotations only supply destructiveHint=true; the description adds real behavioral context beyond that by naming the endpoint (POST /v2/guests, JSON) and warning that emails/phones/addresses must be passed as arrays of objects via the `fields` passthrough rather than typed parameters. It also notes the return (created guest). It does not cover auth/permission requirements or idempotency, so not a 5.

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 compact sentences, front-loaded with the mutation warning followed by the endpoint and the non-obvious array workaround, and closing with the return value. No filler.

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 mutation tool with no output schema, the description closes the important gaps: it flags the mutation, gives the endpoint, explains the array passthrough quirk, and states the return value. It omits whether target fields are required or any permission requirements, but nothing critical to calling the tool is missing.

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 the baseline is 3, but the description adds meaning the schema lacks: the `fields` passthrough is the way to send array-shaped data, illustrated with a concrete email_addresses example. That clarifies semantics of the otherwise opaque additionalProperties object.

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 ('creates a new guest (contact)') and flags that it mutates OwnerRez data, which immediately separates it from the get_/list_/update_ siblings. An agent can identify the operation without opening the schema.

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 by 'creates a new guest' and the API route is given, but there is no explicit when-to-use vs alternative guidance (e.g., use update_guest for existing contacts, or the array-passthrough constraint applies only at create time). The array handling hint is genuinely useful but is a how-to, not a when-to-use rule.

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