create_carrier_subscriber

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

No annotations are provided, so the description carries the full burden. It does disclose the safety mechanism (dry_run preview vs confirm to apply) and the return value, which is genuine behavioral context. However, it omits permissions/auth needs, idempotency behavior, what happens on conflicting subscriber_number, and side effects of plan_id/host_id assignment.

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?

Purpose statement is front-loaded, then a scannable Args block, then Returns. No filler sentences. The list is somewhat mechanical and repeats schema field names, but it earns most of its length through the added constraints.

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?

With an output schema present, the description need not explain return structure, and it correctly just says it returns the created subscriber. It covers params and the confirm/dry_run gate well. Remaining gap: no discussion of how plan_id/host_id interact with the dedicated assign/attach sibling tools, and the stray 'settings' arg is unexplained.

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 only 9% (effectively just controller), so the description must compensate and largely does: it glosses all ten user-facing fields and adds constraints not in the schema, e.g. subscriber_number is '1-32 characters, required'. It even lists 'settings' which is absent from the schema properties, a minor inconsistency, and does not mention controller (left to the schema).

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?

Opens with a specific verb+resource: 'Create a UniFi Carrier Fabric subscriber.' An agent immediately knows the operation and domain. It does not differentiate from siblings like update_carrier_subscriber, suspend_carrier_subscriber, or attach_carrier_subscriber_host, so it stops short of a 5.

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?

There is no explicit when-to-use/when-not section or alternative routing, but the confirm/dry_run annotations ('Must be true to apply the change (required unless dry_run)', 'Preview the change without applying it') implicitly describe the intended mutation workflow. Useful but not a substitute for real usage guidance.

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