update_carrier_subscriber

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

With no annotations, the description carries the full burden and does so well: it discloses that only provided fields are sent, that absent fields are left unchanged, and that explicit nulls are not transmitted by this tool (clearing requires the direct API). It omits permission/auth requirements and rate limits, but the mutation semantics are unusually well exposed.

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 docstring is reasonably front-loaded with the key semantics first. However, the point about only provided fields being sent is stated twice, and the 'Returns' section is redundant given an output schema exists, adding length without value.

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 an 11-parameter mutation tool with no annotations, it covers field semantics and the dry_run/confirm gate adequately, and the return value is documented by the output schema. It leaves a real gap around sibling routing (plan_id/host_id vs. the dedicated assign/attach tools) and any authorization requirements.

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% (just 'controller'), so the schema does almost none of the work. The description compensates by listing and briefly explaining every argument, including the non-obvious confirm/dry_run contract and the metadata dictionary. Definitions are terse but add real meaning beyond the bare 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?

States a specific verb+resource ('Update a UniFi Carrier Fabric subscriber'), which is clear and distinct from siblings like create_carrier_subscriber or suspend_carrier_subscriber. It doesn't, however, differentiate itself from assign_carrier_subscriber_plan or attach_carrier_subscriber_host even though it also accepts plan_id and host_id.

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 explains the confirm/dry_run workflow ('Must be true to apply the change (required unless dry_run)'), which is genuine usage guidance. But it gives no guidance on when to use this tool versus the overlapping siblings that mutate the same fields (assign_carrier_subscriber_plan, attach_carrier_subscriber_host).

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