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dns

by com.blackveilsecurity

check_mta_sts

Read-onlyIdempotent

Check whether a domain enforces SMTP TLS for inbound mail via MTA-STS, protecting against downgrade attacks. Queries _mta-sts. and fetches the policy file, reports mode (enforce/testing/none) and MX coverage. Use to verify whether inbound SMTP is protected against TLS downgrade or MITM — distinct from check_dane which uses TLSA pinning. Part of the scan_domain audit.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
domainYesDomain to check (e.g., example.com)
formatNoOutput verbosity. Auto-detected if omitted.
force_refreshNoBypass cache and run a fresh check. Useful after DNS changes.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
scoreYes
passedYes
partialNo
categoryYes
findingsYes
checkStatusNo

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnly, idempotent, and non-destructive behaviors. The description adds value by detailing the mechanism: queries _mta-sts.<domain>, fetches the policy file, and reports mode and MX coverage. This goes beyond the annotations but does not contradict them.

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?

Three sentences: first states purpose, second explains mechanism and output, third provides usage guidance and differentiation. Every sentence adds value with no redundancy, perfectly front-loaded.

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?

The tool has 3 well-documented parameters, an output schema, and comprehensive annotations. The description covers purpose, mechanism, output fields, and usage context, making it fully sufficient for an agent to select and invoke the tool 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 description coverage is 100%; all three parameters (domain, format, force_refresh) are documented in the schema. The description does not add new parameter semantics beyond implying the domain is the primary input. Baseline 3 is appropriate.

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?

The description clearly states the tool checks MTA-STS enforcement for a domain, specifies the verb 'Check whether a domain enforces SMTP TLS', and distinguishes from the sibling check_dane by mentioning TLSA pinning, making the purpose specific and unambiguous.

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?

The description explicitly says 'Use to verify whether inbound SMTP is protected against TLS downgrade or MITM — distinct from check_dane which uses TLSA pinning', providing direct guidance on when to use this tool and contrasting it with a closely related alternative.

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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TDQS

A3.6/5.0
Disambiguation4/5

Most tools have clearly distinct purposes, with detailed descriptions that help differentiate overlapping areas (e.g., check_dane vs check_dane_https). However, there are sets of similar tools (brand audit, OSINT, polling) that could cause confusion if descriptions are not carefully read.

Naming Consistency3/5

The naming is mostly readable but inconsistent: many check_* tools follow a verb_noun pattern, but there are also noun_verb names (scan_domain, cymru_asn), bare verbs (generate), and varied patterns for async operations (discover_brand_domains_start vs discover_brand_domains).

Tool Count2/5

With 80 tools, the server feels overstuffed. It covers multiple domains (DNS, email, brand, OSINT, M365) that could benefit from separation. The high number includes many polling/status tools that add overhead.

Completeness3/5

The server covers core DNS and email security checks thoroughly, including many edge cases (e.g., BIMI, MTA-STS, subdomain takeover). However, there are gaps like lack of direct DNS record management and some OSINT tools are restricted to operator deployment, leaving agents with dead ends.

Resources