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

Annotations only declare readOnlyHint=true, but the description goes well beyond that: it enumerates the returned fields, names and explains each warning code, discloses the 60-address self-serve ceiling, explains the price/safeReach relationship, and states the 400 refusal for a bookingDate after the last campaign day. This is unusually rich behavioral disclosure for a read-only tool.

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 safety, then inputs, then returns, then the routing note. Dense but every sentence carries information. It is on the long side and slightly packed, keeping it from a 5.

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 0% schema description coverage, this description still fully explains inputs, return shape, and error behavior. Nothing an agent needs to call it correctly is missing.

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 0%, so the description must carry the full burden, and it does: it defines every parameter in prose (contacts, campaignStart as first campaign day in UTC YYYY-MM-DD, campaignDays, bookingDate as the day you would book and normally today, domainsAlreadyHeld with default and a pointer to infrastructure_status, listIsOwnOptIn with default and meaning). This compensates fully for the empty schema annotations.

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 ('Plan') and resource ('dated outreach campaign') with a concrete example (a fundraising drive), plus the immediate outcome ('get its price'). It also distinguishes itself from the sibling launch_campaign by declaring that checkout and booking are not available. An agent can identify this as a read-only estimation/quotation tool without opening the 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 clear context for use ('Read-only: nothing is booked, charged or changed') and an explicit alternative for the adjacent job ('to book, contact support (contact_operator)'). It also guides input choice ('bookingDate ... normally today'). It stops short of a full when-not-to-use-this-vs-sibling clause, so it lands just under a 5.

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