email_verifierVerify if an email address is valid and deliverable. Checks for proper format, domain validity, and mailbox existence without sending an email.
| Name | Required | Description | Default |
|---|---|---|---|
| Yes | The email address to verify | ||
| webhook_url | No | Optional webhook URL to receive results asynchronously | |
| enrich_mobile | No | Whether to enrich with mobile phone data |
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "data": {}
+ },
+ "required": [
+ "data"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds meaningful behavioral context by stating that it checks three specific aspects and does not send an email. This goes beyond the annotations and gives an agent confidence about side effects and scope.
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 no filler. It front-loads the primary action, then lists the verification checks and the notable non-side-effect. Every sentence earns its place and the structure is easy to parse quickly.
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?
Given the output schema exists and annotations cover read-only behavior, the description is nearly complete. It explains what the tool verifies and that it is non-intrusive. It does not mention asynchronous webhook behavior or mobile enrichment, but those are covered by the input schema descriptions, so no critical gap remains.
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 input schema already documents the email, webhook_url, and enrich_mobile parameters. The description does not add extra meaning for any parameter, which is acceptable because the schema carries the full burden. 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 states a specific verb and resource: 'Verify if an email address is valid and deliverable.' It also details the exact checks performed (format, domain validity, mailbox existence), distinguishing it from sibling tools like email_finder, email_format, and email_enrichment. This is unambiguous and immediately tells an agent what the tool is for.
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 makes the core use case clear: validating an email address without sending an email. It does not explicitly name alternative tools or exclusions, but the wording strongly implies when it should be used. A small improvement would be an explicit contrast with email_finder or email_enrichment.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.