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

Annotations already declare the mutation/idempotency/no-cost safety profile, and the description reinforces cost behavior and reversibility plus return semantics. It does not, however, warn about the destructiveHint=true angle — that moving the DID into a group may displace its previous channel allocation — so the destructive side is under-communicated relative to the annotation.

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?

Front-loaded with purpose and effect, then parameters, then preconditions, then the cost clarification and return value. Each sentence carries distinct information with no filler or repetition.

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, the description correctly covers the return value (DID number and new group, or a readable error) and all call preconditions. The only shortfall is that the destructive/reassignment behavior implied by destructiveHint=true is not spelled out.

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% and both parameters are fully documented there (including the 'must belong to the customer' constraint). The description restates the two parameter names but adds no format or syntax detail beyond what the schema provides, so it meets the baseline rather than exceeding it.

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+target (assign a DID to a Shared Capacity Group) and immediately explains the effect: the DID draws inbound channels from the group's Capacity Pool. It distinguishes itself from siblings by contrasting with buy_capacity_channels and by the unassign counterpart, so an agent can route correctly without opening a 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?

Gives explicit preconditions for use (DID's country must be covered by the Capacity Pool; its DID Group must allow additional channels) and names the alternative that money-spending cases should use ('only buy_capacity_channels spends money'). It clearly frames this as allocation of already-purchased channels rather than a purchase.

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