Validate emails (syntax, MX, disposable, role, typo) and phone numbers before your agent saves them.
Scored across 2 tools
validate_email and validate_phone target completely different contact fields with no overlap. An agent can easily tell which tool to use based on the input type.
Both tools follow the exact same verb_noun pattern (validate_email, validate_phone), making the naming predictable and clean.
Only 2 tools for a contact validation server feels thin; while each tool earns its place, the surface is borderline minimal and could easily support additional contact field validators.
Email and phone are covered, but a contact-linting server would reasonably also validate addresses (a core contact field). This is a notable gap that limits the server's usefulness for full contact data quality.
Check an email address: syntax, MX/A records via DNS-over-HTTPS, disposable domain, role address, free provider, typo suggestion for major providers. No SMTP probing. Uses 1 check.
| Name | Required | Description | Default |
|---|---|---|---|
| Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations the description carries the full burden, and it does real work: it discloses the DNS-over-HTTPS mechanism, explicitly rules out SMTP probing (so mailbox existence is not verified), and states the cost ('Uses 1 check'). It stops short of covering auth requirements, error behavior, or return shape.
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 dense sentence, front-loaded with the verb and resource, followed by the enumerated checks and two short constraint clauses. No filler and no redundancy.
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?
No output schema exists, so the description should say what comes back — a boolean, a score, or per-check results — and it does not, despite listing the individual signals it computes. It is otherwise adequate for a single-parameter read-style tool with no annotations.
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?
One required parameter with 0% schema description coverage. The description implies the input is a raw email string to be checked, but adds no format, normalization, or length guidance beyond that obvious inference, so it only marginally compensates for the empty schema.
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?
States a specific verb (check) and resource (email address) and enumerates exactly which checks are performed: syntax, MX/A records, disposable domain, role address, free provider, typo suggestion. The resource alone distinguishes it from the only sibling, validate_phone.
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 explicit when-to-use statement, no routing to or away from validate_phone, and no stated preconditions. The scope note 'No SMTP probing' hints at what kind of validation result to expect, but it is a behavioral boundary rather than usage guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Parse and validate a phone number: valid, possible, type, region, E.164 and national formats. Uses 1 check.
| Name | Required | Description | Default |
|---|---|---|---|
| phone | Yes | ||
| country | No | ISO 3166-1 alpha-2 default region, e.g. US |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden. It discloses the output shape (valid, possible, type, region, formats) since there is no output schema, which is useful. However it says nothing about rate limits, network/API dependence, failure modes, or what 'Uses 1 check' concretely means.
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 compact sentence that front-loads the verb and lists outputs efficiently. The trailing 'Uses 1 check' is vague and slightly lowers clarity, but overall there is little waste.
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?
Because no output schema exists, the description usefully enumerates the returned fields, which is the right thing to do. But it leaves the required phone parameter format unspecified and omits any behavioral or usage context, so it is only minimally complete for a two-parameter validation tool.
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 50%: 'country' is documented, but the required 'phone' parameter has no description in either place. The description mentions 'region' and 'national formats' only as outputs and adds nothing about the phone input format or how country interacts as a default region.
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?
Specific verb ('parse and validate') plus resource ('a phone number'), and it enumerates the returned aspects (valid, possible, type, region, E.164/national formats). It is clearly a phone validator versus the sibling validate_email, though the differentiation is only by resource, not stated explicitly.
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 when-to-use guidance, no prerequisites, and no alternatives named. An agent gets no help deciding between this and validate_email or when a phone check is warranted. 'Uses 1 check' reads as a technical aside rather than routing guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
validate_emailvalidate_phoneVerify email addresses in real time: deliverability, disposable and role addresses, typo fixes.
Email intelligence for agents: MX, SPF/DKIM/DMARC, disposable/role checks, and a 0-100 score.
Verify addresses, email addresses, and phone numbers with confidence scores.
Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key.
Add one secure layer between your agents and this server.
