Send a test email from a campaign to preview its appearance in recipients' inboxes. Validate formatting and deliverability before the full send.
Send a test email for an existing campaign to preview how it will look in recipients' inboxes.
| Name | Required | Description | Default |
|---|---|---|---|
| apiKey | No | Send16 API key (overrides SEND16_API_KEY env var) | |
| testEmail | Yes | Email address to send the test to | |
| campaignId | Yes | Campaign ID to send test for |
Changes observed during successful MCP inspections.
v0.5.7Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must fully disclose behavior. While it correctly identifies the operation as a test (non-destructive), it lacks details on prerequisites (e.g., campaign must exist and be valid), potential side effects (e.g., rate limits), and whether it affects campaign state.
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 a single clear sentence with no unnecessary words. While it could be slightly more structured (e.g., broken into usage and behavior), it is highly concise and front-loads the key purpose.
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 test tool, the description covers the core purpose and usage. However, it omits expected output (e.g., success message or delivery status) and edge cases (e.g., invalid campaign ID). With no output schema, additional return information would improve completeness.
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 the schema already documents all parameters. The description does not add new parameter information beyond stating it is for an 'existing campaign.' Baseline score 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 clearly states the action ('Send a test email'), the target resource ('an existing campaign'), and the purpose ('to preview how it will look in recipients' inboxes'). It distinguishes itself from sibling tools like 'send_broadcast' (sends to actual recipients) and 'preview_campaign_recipients' (previews who will receive).
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 implies usage context ('to preview how it will look'), suggesting it should be used before final sending. However, it does not explicitly state when to use or avoid this tool, nor does it mention alternatives like 'send_broadcast' for actual sending.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.