Update a draft campaign. Only draft campaigns can be updated.
| Name | Required | Description | Default |
|---|---|---|---|
| fields | Yes | Fields to update,required | |
| api_key | No | MailerCloud API key | |
| campaign_id | Yes | Campaign ID,required |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide the key behavioral signals: readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description adds the draft-only constraint, which is useful, but does not elaborate on side effects, permissions, or error conditions. Given the annotations cover safety, a score of 3 is appropriate.
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 two short sentences with zero fluff. The essential constraint (draft-only) is front-loaded and the entire description is easily parsed by an agent. Every word earns its place.
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 update operation with comprehensive schema coverage and useful annotations, the description conveys the key business rule. It does not explain return values or required permissions, but given no output schema and the annotations covering safety, it is sufficiently complete for correct invocation.
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 100%, so all three parameters (campaign_id, fields, api_key) are already documented in the schema. The description does not add extra meaning beyond what the schema provides, so the baseline of 3 applies.
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 clearly states a specific verb 'Update' and resource 'campaign', and adds a critical scope restriction 'draft campaign'. This distinguishes it from sibling tools like create_campaign or schedule_campaign, making the tool's purpose 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 description explicitly states when the tool can be used ('Only draft campaigns can be updated'), which serves as a clear precondition. However, it does not mention alternatives or when not to use it beyond the draft restriction, so it stops short of full guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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Tool purposes are largely distinct, with clear separation between CRUD operations, analytics, and deliverability tools. Some overlap exists between get_campaign, analyze_campaign, and campaign_health_dashboard, but descriptions clarify scope sufficiently.
Most tools follow a consistent verb_noun pattern (list_, get_, create_, update_, delete_, send_). Minor exceptions like campaign_health_dashboard and engagement_funnel are descriptive but break the pattern.
With 47 tools, this is a very large surface area. While the variety reflects the breadth of email marketing operations, the count exceeds what is typically manageable and suggests potential redundancy or over-scoping.
The tool set covers most core workflows: contact/list management, campaign lifecycle, templates, webhooks, analytics, and transactional email. Minor gaps like no delete for templates or tags are acceptable but not fatal.
