Crate pmcp_code_mode 

Code Mode - LLM-generated query validation and execution.

This crate provides the infrastructure for “Code Mode”, which allows MCP clients to generate and execute structured queries (GraphQL, SQL, REST) with a validation pipeline that ensures security and provides human-readable explanations.

Architecture

describe_schema() → LLM generates code → validate_code() → user approval → execute_code()

Key Components

• Validation Pipeline: Parse → Policy Check → Security Analysis → Explanation → Token
• Approval Tokens: HMAC-signed tokens binding code hash to validation result
• Explanations: Template-based business-language descriptions of queries
• Policy Evaluation: Pluggable trait for Cedar/AVP/custom policy engines

Example Usage

use pmcp_code_mode::{
    CodeModeConfig, ValidationPipeline, ValidationContext
};

// Create a validation pipeline
let config = CodeModeConfig::enabled();
let pipeline = ValidationPipeline::new(config, b"secret-key".to_vec());

// Validate a query
let context = ValidationContext::new("user-123", "session-456", "schema-hash", "perms-hash");
let result = pipeline.validate_graphql_query("query { users { id name } }", &context)?;

Re-exports

pub use config::CodeModeConfig;

pub use validation::ValidationContext;

pub use validation::ValidationPipeline;

pub use templates::TemplateContext;

pub use handler::format_error_response;

pub use handler::format_execution_error;

pub use handler::CodeModeHandler;

pub use handler::CodeModeToolBuilder;

pub use handler::ExecuteCodeInput;

pub use handler::ValidateCodeInput;

pub use handler::ValidationResponse;

pub use policy::AuthorizationDecision;

pub use policy::OperationEntity;

pub use policy::PolicyEvaluationError;

pub use policy::PolicyEvaluator;

pub use policy::ServerConfigEntity;

pub use policy::get_baseline_policies;

pub use policy::get_code_mode_schema_json;

pub use schema_exposure::CodeModeExposurePolicy;

pub use schema_exposure::DerivationMetadata;

pub use schema_exposure::DerivationStats;

pub use schema_exposure::DerivedSchema;

pub use schema_exposure::ExposureMode;

pub use schema_exposure::FilterReason;

pub use schema_exposure::FilteredOperation;

pub use schema_exposure::GlobalBlocklist;

pub use schema_exposure::McpExposurePolicy;

pub use schema_exposure::MethodExposurePolicy;

pub use schema_exposure::Operation;

pub use schema_exposure::OperationCategory;

pub use schema_exposure::OperationDetails;

pub use schema_exposure::OperationParameter;

pub use schema_exposure::OperationRiskLevel;

pub use schema_exposure::SchemaDeriver;

pub use schema_exposure::SchemaFormat;

pub use schema_exposure::SchemaMetadata;

pub use schema_exposure::SchemaSource;

pub use schema_exposure::ToolExposurePolicy;

pub use schema_exposure::ToolOverride;

Modules

config

Code Mode configuration.

handler

Code Mode Handler trait for unified soft-disable and tool management.

policy

Policy evaluation for Code Mode.

policy_annotations

Policy annotation parser for Cedar policies.

schema_exposure

Schema Exposure Architecture for MCP Built-in Servers.

templates

Code Mode instruction and policy templates.

validation

Validation pipeline for Code Mode.

Structs

ApprovalToken

Approval token that authorizes code execution.

CodeLocation

Location in source code.

GraphQLQueryInfo

Information extracted from a parsed GraphQL query.

GraphQLValidator

GraphQL query validator.

HmacTokenGenerator

HMAC-based token generator for MVP.

PolicyViolation

A policy violation found during validation.

SecurityAnalysis

Security analysis of code.

SecurityIssue

Potential security issues found during analysis.

TemplateExplanationGenerator

Template-based explanation generator for MVP.

ValidationMetadata

Detailed metadata about a validation.

ValidationResult

Result of validating code through the pipeline.

Enums

CodeType

Type of code being validated/executed.

Complexity

Estimated complexity of a query.

ExecutionError

Errors that can occur during execution.

GraphQLOperationType

GraphQL operation type.

RiskLevel

Risk level assessed for a query or workflow.

SecurityIssueType

Types of security issues.

UnifiedAction

Unified action model that maps to business permissions. Works consistently across GraphQL, OpenAPI, and SQL servers.

ValidationError

Errors that can occur during validation.

Traits

ExplanationGenerator

Trait for generating human-readable explanations.

TokenGenerator

Trait for token generators.

Functions

canonicalize_code

Canonicalize code for consistent hashing.

compute_context_hash

Compute a context hash from schema and permissions.

hash_code

Compute the SHA-256 hash of canonicalized code.