Retrieve the schema definition for the specified schema version. REQUIREMENTS: - You MUST use this tool to get complete schema definitions before implementing handlers - You MUST use this tool when implementing Lambda functions that consume events from EventBridge - You MUST use the returned sch...
Part of the AWS Serverless MCP Server MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents call describe_schema to retrieve information from AWS Serverless MCP Server without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though describe_schema only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
tools:
describe_schema:
rules:
- action: allowSee the full AWS Serverless MCP Server policy for all 32 tools.
Agents calling read-class tools like describe_schema have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Read risk category across the catalogue. The same policy patterns (rate-limit, allow) apply to each.
Retrieve the schema definition for the specified schema version. REQUIREMENTS: - You MUST use this tool to get complete schema definitions before implementing handlers - You MUST use this tool when implementing Lambda functions that consume events from EventBridge - You MUST use the returned schema structure for type-safe event handling - You SHOULD use the latest schema version unless specifically required otherwise - You MUST validate all required fields defined in the schema USE CASES: 1. Lambda Function Handlers with EventBridge: You MUST: - CRITICAL: Required for Lambda functions consuming events from EventBridge - Implement handlers using the exact event structure - Validate all required fields defined in schema - Handle optional fields appropriately - Ensure type safety for EventBridge-sourced events You SHOULD: - Generate strongly typed code based on schema - Implement error handling for missing fields - Document any assumptions about structure 2. EventBridge Rules: You MUST: - Create patterns that exactly match schema - Use correct field names and value types - Include all required fields in patterns You SHOULD: - Test patterns against sample events - Document pattern matching logic - Consider schema versions in design The schema content provides complete event structure with all fields and types, ensuring correct event handling.. It is categorised as a Read tool in the AWS Serverless MCP Server MCP Server, which means it retrieves data without modifying state.
Add a rule in your Intercept YAML policy under the tools section for describe_schema. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the AWS Serverless MCP Server MCP server.
describe_schema is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the describe_schema rule in your Intercept policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the Intercept policy for describe_schema. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
describe_schema is provided by the AWS Serverless MCP Server MCP server (awslabs.aws-serverless-mcp-server). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic policy on every MCP tool call. Per-identity grants. Full audit log.