Skip to main content
Glama
OrygnsCode

opa-mcp-server

by OrygnsCode
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

Evaluate Rego with execution trace

rego_eval_with_explain

Evaluate a Rego query with full OPA explain tracing and return raw trace events with AST nodes alongside the result, so you can debug policy decisions at the event level.

Instructions

Evaluate with --explain=full and return OPA's raw trace events (with their AST nodes) alongside the result. For a readable trace use rego_explain_decision, which renders the same events as lines. Raw events are large: over the response cap the bound-variable values are dropped first, then trailing events (explanationTruncated), and the result is kept.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
inputNoInline input document.
pathsNoPolicy / data file or directory paths. Each must be inside an allowed root.
queryYesRego query to evaluate, e.g. "data.example.allow".
sourceNoInline Rego policy source. Optional: without `source` or `paths` the query runs on its own, which is enough to try a built-in or an expression.
partialNoRun partial evaluation rather than full evaluation.
unknownsNoRefs to treat as unknown during partial evaluation.
inputPathNoPath to a JSON input file. Mutually exclusive with `input`.
v0CompatibleNoRead the policy as Rego v0 (`--v0-compatible`), the syntax OPA used before 1.0: rules without `if`, partial sets as `deny[msg] { ... }`. Needed for a policy that has not been migrated, which OPA 1.x otherwise refuses to load. Where the tool also takes a query, the query is read as v0 too, with the future keywords imported so `in`, `every` and `some x in` still work in it.
strictBuiltinErrorsNoTreat builtin errors as fatal instead of returning undefined.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.8.0
    • changedInput schema / properties / v0Compatible / description
      Previous value: -"Read the policy as Rego v0 (`--v0-compatible`), the syntax OPA used before 1.0: rules without `if`, partial sets as `deny[msg] { ... }`. Needed for a policy that has not been migrated, which OPA 1.x otherwise refuses to load."New value: +"Read the policy as Rego v0 (`--v0-compatible`), the syntax OPA used before 1.0: rules without `if`, partial sets as `deny[msg] { ... }`. Needed for a policy that has not been migrated, which OPA 1.x otherwise refuses to load. Where the tool also takes a query, the query is read as v0 too, with the future keywords imported so `in`, `every` and `some x in` still work in it."
  2. Changed2 schema fields changedv0.7.0
    • changedInput schema / properties / source / description
      Previous value: -"Inline Rego policy source. Mutually exclusive with `paths`."New value: +"Inline Rego policy source. Optional: without `source` or `paths` the query runs on its own, which is enough to try a built-in or an expression."
    • addedInput schema / properties / v0Compatible
      Added value: +{
+  "description": "Read the policy as Rego v0 (`--v0-compatible`), the syntax OPA used before 1.0: rules without `if`, partial sets as `deny[msg] { ... }`. Needed for a policy that has not been migrated, which OPA 1.x otherwise refuses to load.",
+  "type": "boolean"
+}
  3. Addedv0.1.13
  4. Removedv0.1.5
  5. Addedv0.1.2
  6. Removedv0.1.1
  7. First observedv0.1.0

TDQS

A4.2/5.0
Behavior4/5

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

Annotations only supply readOnlyHint=false and openWorldHint=true; the description adds genuinely useful behavioral detail beyond them — raw events are large, bound-variable values are dropped first under the response cap, then trailing events, with an `explanationTruncated` marker while the result is preserved. It does not address why evaluation is non-read-only or any execution/security implications, so it stops short of a 5.

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 dense sentences, each earning its place: what it does, which sibling to use instead, and the truncation behavior. The differentiation and truncation notice are front-loaded and there is no filler.

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?

For a nine-parameter tool with no output schema, the description carries the important output-shape information (raw events, truncation contract) and routes to the readable alternative. Annotations cover the safety profile, so overall it is sufficiently complete, with only minor room for noting execution semantics.

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%, so all nine parameters are already documented in the schema (including the mutually exclusive `input`/`inputPath`, `v0Compatible`, and `partial`/`unknowns`). The description adds nothing about parameter syntax or formats, so the baseline 3 applies.

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 (evaluate Rego) and pins down the exact mode: `--explain=full` returning OPA's raw trace events with AST nodes. It explicitly distinguishes itself from the sibling `rego_explain_decision`, so an agent can route between the two without opening either schema.

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?

Names the alternative `rego_explain_decision` and the condition that selects it (readable, line-oriented trace), which implicitly tells the agent when to pick this raw-output variant. It does not, however, cover when to choose this over the plain `rego_eval` / `rego_eval_with_profile` / `rego_eval_with_coverage` siblings.

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

Deploy Server

Other Tools