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Conftest test

conftest_test

Evaluate Kubernetes, Terraform, Docker, Helm, or YAML/JSON/HCL/TOML configs against Rego policies and return per-file pass/fail/warn results to pinpoint failed rules.

Instructions

Evaluate configuration files (Kubernetes manifests, Terraform plans, Dockerfiles, Helm charts, or any YAML/JSON/HCL/TOML/INI) against Rego policies using conftest test. Returns per-file, per-namespace pass/fail/warn results so you can pinpoint exactly which policy rules fired. Requires conftest on PATH or CONFTEST_BINARY set; returns CONFTEST_NOT_FOUND otherwise. Provide config via files (disk paths) or inlineConfig (inline string). Provide policy via policy (disk path) or inlinePolicy (inline Rego source). Omit policy and inlinePolicy to use conftest's default ./policy directory. Policies are executed by conftest and can call OPA built-ins such as http.send.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataNoPaths to directories from which additional data will be loaded for the Rego policies. Each path must be inside an allowed root.
filesNoFilesystem paths to configuration files to evaluate (YAML, JSON, HCL, Dockerfile, etc.). Each path must be inside an allowed root (OPA_MCP_ALLOWED_PATHS). Mutually exclusive with `inlineConfig`.
parserNoForce a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). One of: cue, cyclonedx, dockerfile, dotenv, edn, groovy, hcl1, hcl2, hocon, ignore, ini, json, jsonc, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. For `inlineConfig`, prefer `inlineConfigParser`.
policyNoPath to a directory or file containing Rego policies. Must be inside an allowed root (OPA_MCP_ALLOWED_PATHS). Mutually exclusive with `inlinePolicy`. Omit to let conftest use its default `./policy` directory.
combineNoCombine all configuration files into a single input document before evaluating. Useful when policies need to inspect relationships across multiple files.
namespaceNoRego namespace (package name) to test against. Defaults to `main`. Use `allNamespaces: true` to test all discovered namespaces instead.
failOnWarnNoReturn `passed: false` even when only warnings (no hard failures) are present.
inlineConfigNoInline configuration content to evaluate (e.g. a Kubernetes manifest as a YAML string). Mutually exclusive with `files`. Defaults to YAML format; set `inlineConfigParser` to override.
inlinePolicyNoInline Rego policy source. Written to a temporary directory and passed as `--policy`. The policy should declare `package main` (or match the `namespace` parameter). Mutually exclusive with `policy`.
v0CompatibleNoRead the policies as Rego v0 (`--rego-version v0`), the syntax before OPA 1.0: rules without `if`, `deny[msg] { ... }`. conftest reads v1 by default and refuses such a policy.
allNamespacesNoTest policies found in all discovered namespaces. Overrides `namespace`.
inlineConfigParserNoParser to use for `inlineConfig`. One of: cue, cyclonedx, dockerfile, dotenv, edn, groovy, hcl1, hcl2, hocon, ignore, ini, json, jsonc, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. Defaults to yaml. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set).

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.8.0
    • addedInput schema / properties / v0Compatible
      Added value: +{
      +  "description": "Read the policies as Rego v0 (`--rego-version v0`), the syntax before OPA 1.0: rules without `if`, `deny[msg] { ... }`. conftest reads v1 by default and refuses such a policy.",
      +  "type": "boolean"
      +}
  2. Changed4 schema fields changedv0.7.0
    • changedInput schema / properties / inlineConfigParser / description
      Previous value: -"Parser to use for `inlineConfig`. One of: cue, dockerfile, dotenv, edn, hcl1, hcl2, hocon, ignore, ini, json, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. Defaults to yaml. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set)."New value: +"Parser to use for `inlineConfig`. One of: cue, cyclonedx, dockerfile, dotenv, edn, groovy, hcl1, hcl2, hocon, ignore, ini, json, jsonc, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. Defaults to yaml. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set)."
    • changedInput schema / properties / inlineConfigParser / enum
      Previous value: -[
      -  "cue",
      -  "dockerfile",
      -  "dotenv",
      -  "edn",
      -  "hcl1",
      -  "hcl2",
      -  "hocon",
      -  "ignore",
      -  "ini",
      -  "json",
      -  "jsonnet",
      -  "nginx",
      -  "properties",
      -  "spdx",
      -  "textproto",
      -  "toml",
      -  "vcl",
      -  "xml",
      -  "yaml"
      -]New value: +[
      +  "cue",
      +  "cyclonedx",
      +  "dockerfile",
      +  "dotenv",
      +  "edn",
      +  "groovy",
      +  "hcl1",
      +  "hcl2",
      +  "hocon",
      +  "ignore",
      +  "ini",
      +  "json",
      +  "jsonc",
      +  "jsonnet",
      +  "nginx",
      +  "properties",
      +  "spdx",
      +  "textproto",
      +  "toml",
      +  "vcl",
      +  "xml",
      +  "yaml"
      +]
    • changedInput schema / properties / parser / description
      Previous value: -"Force a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). One of: cue, dockerfile, dotenv, edn, hcl1, hcl2, hocon, ignore, ini, json, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. For `inlineConfig`, prefer `inlineConfigParser`."New value: +"Force a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). One of: cue, cyclonedx, dockerfile, dotenv, edn, groovy, hcl1, hcl2, hocon, ignore, ini, json, jsonc, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. For `inlineConfig`, prefer `inlineConfigParser`."
    • changedInput schema / properties / parser / enum
      Previous value: -[
      -  "cue",
      -  "dockerfile",
      -  "dotenv",
      -  "edn",
      -  "hcl1",
      -  "hcl2",
      -  "hocon",
      -  "ignore",
      -  "ini",
      -  "json",
      -  "jsonnet",
      -  "nginx",
      -  "properties",
      -  "spdx",
      -  "textproto",
      -  "toml",
      -  "vcl",
      -  "xml",
      -  "yaml"
      -]New value: +[
      +  "cue",
      +  "cyclonedx",
      +  "dockerfile",
      +  "dotenv",
      +  "edn",
      +  "groovy",
      +  "hcl1",
      +  "hcl2",
      +  "hocon",
      +  "ignore",
      +  "ini",
      +  "json",
      +  "jsonc",
      +  "jsonnet",
      +  "nginx",
      +  "properties",
      +  "spdx",
      +  "textproto",
      +  "toml",
      +  "vcl",
      +  "xml",
      +  "yaml"
      +]
  3. Changed4 schema fields changedv0.5.0
    • changedInput schema / properties / inlineConfigParser / description
      Previous value: -"Parser to use for `inlineConfig`. Valid values: yaml (default), json, toml, hcl1, hcl2, ini, xml, dotenv, cue, jsonnet, properties, edn, hocon, dockerfile. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set)."New value: +"Parser to use for `inlineConfig`. One of: cue, dockerfile, dotenv, edn, hcl1, hcl2, hocon, ignore, ini, json, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. Defaults to yaml. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set)."
    • addedInput schema / properties / inlineConfigParser / enum
      Added value: +[
      +  "cue",
      +  "dockerfile",
      +  "dotenv",
      +  "edn",
      +  "hcl1",
      +  "hcl2",
      +  "hocon",
      +  "ignore",
      +  "ini",
      +  "json",
      +  "jsonnet",
      +  "nginx",
      +  "properties",
      +  "spdx",
      +  "textproto",
      +  "toml",
      +  "vcl",
      +  "xml",
      +  "yaml"
      +]
    • changedInput schema / properties / parser / description
      Previous value: -"Force a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). Valid values: yaml, json, toml, hcl1, hcl2, ini, xml, dotenv, cue, jsonnet, properties, edn, hocon, dockerfile. For `inlineConfig`, prefer `inlineConfigParser`."New value: +"Force a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). One of: cue, dockerfile, dotenv, edn, hcl1, hcl2, hocon, ignore, ini, json, jsonnet, nginx, properties, spdx, textproto, toml, vcl, xml, yaml. For `inlineConfig`, prefer `inlineConfigParser`."
    • addedInput schema / properties / parser / enum
      Added value: +[
      +  "cue",
      +  "dockerfile",
      +  "dotenv",
      +  "edn",
      +  "hcl1",
      +  "hcl2",
      +  "hocon",
      +  "ignore",
      +  "ini",
      +  "json",
      +  "jsonnet",
      +  "nginx",
      +  "properties",
      +  "spdx",
      +  "textproto",
      +  "toml",
      +  "vcl",
      +  "xml",
      +  "yaml"
      +]
  4. Changed2 schema fields changedv0.1.20
    • changedInput schema / properties / inlineConfigParser / description
      Previous value: -"Parser to use for `inlineConfig`. Valid values: yaml (default), json, toml, hcl1, hcl2, ini, xml, dotenv, cue, jsonnet, properties, dockerfile. Ignored when `files` is used (conftest infers the parser from each file's extension)."New value: +"Parser to use for `inlineConfig`. Valid values: yaml (default), json, toml, hcl1, hcl2, ini, xml, dotenv, cue, jsonnet, properties, edn, hocon, dockerfile. Ignored when `files` is used (conftest infers the parser from each file's extension, unless `parser` is set)."
    • addedInput schema / properties / parser
      Added value: +{
      +  "description": "Force a specific parser for all input `files` via conftest's global `--parser` flag, overriding extension-based detection. Useful for files whose extension does not match their format (e.g. parse a `.tfstate` file as `json`). Valid values: yaml, json, toml, hcl1, hcl2, ini, xml, dotenv, cue, jsonnet, properties, edn, hocon, dockerfile. For `inlineConfig`, prefer `inlineConfigParser`.",
      +  "type": "string"
      +}
  5. Addedv0.1.13

TDQS

A4.6/5.0
Behavior5/5

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

With readOnlyHint=false and openWorldHint=true already declared, the description goes further: it discloses the binary prerequisite and failure mode, the mutual-exclusivity rules for policy/config sources, the default ./policy fallback, the per-file/per-namespace pass/fail/warn return shape, and that policies can invoke OPA built-ins like http.send (network egress).

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

Conciseness4/5

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

Front-loaded with the core action and return contract, then prerequisites and source-selection rules. It is dense and somewhat long for a description, but nearly every sentence carries non-schema information.

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?

For a 12-parameter, zero-required, no-output-schema tool, the description covers invocation prerequisites, input source selection, defaults, return structure, and execution environment. An agent has enough to call it correctly without opening the schema.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline is 3; the description earns extra by spelling out the paired sources (`files` vs `inlineConfig`, `policy` vs `inlinePolicy`), the omit-policy default, and the parser/inlineConfigParser split. Most per-parameter detail, however, remains in the schema.

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?

Starts with a specific verb+resource ('Evaluate configuration files') and enumerates the accepted input formats, then names the underlying command. It also distinguishes itself from siblings like rego_test/conftest_verify by naming the conftest execution path and the file-vs-string input model.

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

Usage Guidelines4/5

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

Explains when this applies (config files vs Rego policies) and states the prerequisite (`conftest` on PATH or `CONFTEST_BINARY`), plus the CONFTEST_NOT_FOUND outcome. It does not explicitly compare against siblings such as conftest_verify or rego_test, so no exclusions are given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.