preview_messagePreview personalized outreach messages by filling template placeholders such as first_name, company, and custom fields, with fallback values for missing data before sending.
Fill {{first_name}}, {{name}}, {{company}} and any extra {{placeholders}} (fallbacks: {{first_name|there}}).
| Name | Required | Description | Default |
|---|---|---|---|
| extra | No | ||
| company | No | ||
| template | Yes | ||
| recipient_name | No |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, yet it never discloses that this is a safe/non-mutating render step, nor what happens with unresolved placeholders. It adds only syntax-level detail (fallback form '{{first_name|there}}'), which is a small piece of behavioral context.
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?
It is very short with no filler, but it is a sentence fragment rather than a front-loaded purpose statement, so its brevity comes at the cost of the essential information.
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?
An output schema exists so return values need not be described, but the description omits the core behavior (no-send preview), the parameter-to-placeholder mapping, and how 'extra' merges with the template. For a 4-parameter tool with zero schema coverage, this is insufficient.
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 0%, so the description must explain all four parameters. It hints at company and extra placeholders, but never connects the 'recipient_name' parameter to the {{first_name}}/{{name}} tokens it names, and never explains that 'extra' is a key-value map of custom placeholder values.
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 is a fragment about template placeholder syntax, not a statement of what the tool does. It never says the tool renders/previews a message without sending it, so an agent must infer the verb and resource from the name alone.
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?
There is no guidance on when to use this versus send_email or send_whatsapp, and no explicit statement that this is a non-sending preview. The agent is left to guess whether calling it has side effects.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.