Blackwood State

Email list check

blackwood_email_batch

Read-onlyIdempotent

Use when you need bulk email validation, email list verification or to verify email lists before a send or import. Do not use for one address (email-check is cheaper), proving a mailbox exists (no SMTP probe) or sending email. Returns JSON checking up to 20 email addresses in one call: syntax, MX records, disposable, free and role flags, SPF, DMARC and a verdict each, plus counts by verdict for 0.02 USDC per call. Typical response time 2500 ms (p95). Category: Data.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "emails": "<emails>"
    },
    "name": "blackwood_email_batch"
  }
}

Input Schema

Name	Required	Description	Default
`emails`	Yes	Email addresses to check, 1 to 20, e.g. ["jane@example.com", "info@ietf.org"]
`response_format`	No	concise (the default when omitted) keeps the JSON short: long fields such as base64 images or audio come back as separate image/audio content blocks and other long strings are cut with a marker; detailed returns the full JSON

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 17, 2026

TDQS

A4.7/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the bar is lower. The description adds substantive behavioral context beyond that: no SMTP probe limitation, per-call cost (0.02 USDC), p95 latency (2500 ms), and the 20-address batch cap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the usage condition and exclusion before the return-value details; every sentence (use case, exclusions, return contents, cost/latency) carries distinct information with no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present the description need not enumerate return fields, yet it still summarizes the verdict structure and counts. Combined with rich annotations and full parameter coverage, an agent has everything needed to invoke correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so both parameters (emails and response_format) are already documented in the schema, establishing a baseline of 3. The description reiterates the 20-address cap but adds no syntax, format, or breaking-down detail beyond what the schema states.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (bulk email validation / email list verification) and explicitly distinguishes itself from the sibling blackwood_email_check by rejecting single-address use. An agent can identify the tool's domain without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly names when to use it ('before a send or import'), when not to use it ('one address', 'proving a mailbox exists', 'sending email'), and points to the cheaper alternative email-check. Nothing is left to inference.

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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