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

Annotations flag this as a destructive, non-idempotent, open-world write, and the description adds substantive detail beyond them: phone normalization via the campaign calling code, duplicates and invalid numbers counted rather than added, and do-not-call numbers skipped and never called. This is exactly the operational fallout an agent needs before firing a bulk write.

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?

One dense paragraph, front-loaded with the write verb and campaign scope, with zero filler sentences. The semicolon-chained clauses are information-rich but slightly packed, which keeps it just short of ideal.

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?

No output schema exists, but the description signals that results are counts (duplicates/invalid counted, DNC recorded as skipped), which is enough for an agent to interpret the response. The only meaningful gap is the unstated relationship between the two campaign identifier parameters.

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 0% and the targets array has an untyped item schema, so the description carries the burden — and it does, spelling out the {phone, name, vars} item shape plus the bare-phone shortcut and naming both campaign selectors. It omits whether one of voip_campaign_id/voip_campaign_uuid is required or which wins when both are supplied.

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: adds people/targets to a VOIP campaign, identified by id or uuid. It is immediately distinguishable from siblings like add_email_list_members (different channel) and create_voip_campaign (creates rather than populates).

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 clear precondition (campaign must not have ended) and a hard batch cap (at most 500 at a time), which tells the agent when the call is valid. It does not explicitly name alternatives such as add_voip_optouts or the email-list import, so routing guidance is implied rather than complete.

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