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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and no destructive action. The description adds the important exclusion list behavior and the truncation caveat, plus the cached/unpaginated sibling behavior, giving practical operational transparency beyond the annotation flags.

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 description is longer than typical but every sentence earns its place: it front-loads the starting instruction, lists return fields, gives a mandatory action, names alternatives, and closes with a workflow. It is dense but well-structured and skips filler.

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 fully describes the meaningful return entities (campaign context, capacity, send queue, exclude_domains, truncation flag) and provides actionable next steps. For a single-parameter tool with no output schema, this is complete enough to guide correct invocation and follow-through.

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 the only parameter, campaign_id, is self-explanatory. The description reinforces its meaning ('top up') but does not add significant new syntax or format details, so the baseline of 3 is appropriate.

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?

The description opens with 'START HERE when adding more websites to an existing campaign', a specific verb and resource. It clearly states what the tool returns and distinguishes itself from sibling discovery tools by framing it as the campaign-context entry point.

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 explicitly says when to use the tool ('START HERE'), provides a required filtering step against exclude_domains, names alternatives (get_similar_domains, get_link_intersect, get_platform_domains) when the gap is exhausted, and ends with the full workflow through outreach_add_contacts and outreach_launch_campaign.

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