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opa-mcp-server

Conftest test

conftest_test
Read-onlyIdempotent

Evaluate Kubernetes manifests, Terraform plans, or any YAML/JSON/HCL files against Rego policies. Returns per-file pass/fail/warn results to pinpoint policy rule violations.

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.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
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`.
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.
inlineConfigParserNoParser 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).
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.
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`.
namespaceNoRego namespace (package name) to test against. Defaults to `main`. Use `allNamespaces: true` to test all discovered namespaces instead.
allNamespacesNoTest policies found in all discovered namespaces. Overrides `namespace`.
dataNoPaths to directories from which additional data will be loaded for the Rego policies. Each path must be inside an allowed root.
combineNoCombine all configuration files into a single input document before evaluating. Useful when policies need to inspect relationships across multiple files.
failOnWarnNoReturn `passed: false` even when only warnings (no hard failures) are present.
Behavior5/5

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

The description adds behavioral context beyond the annotations: it explains that missing conftest returns CONFTEST_NOT_FOUND, describes the return format, and mentions allowed path restrictions. This complements the readOnlyHint, destructiveHint, and idempotentHint annotations.

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?

The description is concise (three sentences) with a clear front-loaded purpose, followed by essential details. Every sentence contributes value without redundancy.

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

Completeness4/5

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

Given 10 parameters and no output schema, the description covers prerequisites, alternate input methods, and return format. It could be improved by detailing the structure of the result object, but the current level is sufficient for basic usage.

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 description coverage is 100%, and the tool description adds high-level usage semantics like mutually exclusive pairs, default values, and behavior for parser inference. While individual parameter descriptions are already detailed, the summary ties them together effectively.

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 evaluates configuration files against Rego policies using `conftest test`, specifies supported file types, and distinguishes from sibling conftest tools like `conftest_pull` and `conftest_push`. It also clarifies the return format (per-file, per-namespace pass/fail/warn).

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?

The description mentions prerequisites (conftest on PATH), explains mutually exclusive parameter pairs (files vs inlineConfig, policy vs inlinePolicy), and notes defaults (namespace 'main', default policy directory). However, it does not explicitly advise when to use this tool versus alternatives like `rego_eval` or `rego_test` for pure policy evaluation.

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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