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

Annotations already declare a non-read, non-destructive, non-idempotent, closed-world mutation. The description goes beyond them by disclosing the empty-value stop behavior and the 'verified number' and 'Pro plan' preconditions, which are not in the structured data. It stops short of describing reversibility or failure modes.

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?

Two front-loaded sentences with no filler; the mutation behavior comes first and the plan constraint is a compact trailing note. Every clause carries information.

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 no output schema and two parameters (one undocumented), the description is adequate on the mutation itself but leaves the identity_id target and any return/confirmation behavior unaddressed. Annotations cover the safety profile, so the remaining gaps are moderate rather than severe.

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 50%: forward_to is documented with the empty-to-stop semantics, which the description reinforces, but identity_id has no description in either the schema or the prose. The description adds meaning for one parameter while leaving the other entirely opaque.

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: pointing a verified number at a business number on this seat, plus the stop behavior. It cleanly separates update_forwarding from its read counterpart but never names get_forwarding or any other sibling, so it is clear without being explicitly differentiated.

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?

Gives a usable condition (pass an empty forward_to to stop) and a plan gate ('Pro plan'), which is real when-to-use guidance. However it never names the read alternative get_forwarding or states prerequisites like number verification requirements beyond the passing mention.

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