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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering safety profile. The description adds behavioral context by listing what the tool returns (name, status, subject line, recipient list, performance stats, send history), which goes beyond the annotations. No contradictions.

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?

A single, well-structured sentence that starts with the verb and resource, then succinctly lists the major return contents. No wasted words, every phrase adds value.

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?

For a simple get-by-ID tool with only 2 fully documented parameters, rich annotations, and an output schema, the description is complete. It doesn't need to explain return values in depth since the output schema exists, and the listed return fields are sufficient.

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%, with both parameters (_apiKey and campaign_id) already described. The description adds only 'by ID' which slightly reinforces campaign_id's purpose but does not meaningfully enhance the schema's parameter semantics. Baseline 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 uses the specific verb 'Get' with the resource 'a campaign's full details by ID', clearly distinguishing this from sibling tools like klaviyo_list_campaigns (listing) and klaviyo_get_profile (profiles). It also enumerates the key data returned, making the tool's scope unambiguous.

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 phrase 'by ID' and 'full details' clearly imply usage when a specific campaign ID is known and comprehensive information is needed. It does not explicitly state exclusions or direct alternatives, but the context plus sibling names make the appropriate use case clear. No misleading guidance.

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