Design, build, deploy, test, and debug serverless applications with AWS Lambda. Triggers on phrases like: Lambda function, event source, serverless application, API Gateway, EventBridge, Step Functions, serverless API, event-driven architecture, Lambda trigger. For deploying non-serverless apps to AWS, use deploy-on-aws plugin instead.
Design, build, deploy, and debug serverless applications with AWS serverless services. This skill provides access to serverless development guidance through the AWS Serverless MCP Server, helping you to build production-ready serverless applications with best practices built-in.
Use SAM CLI for project initialization and deployment, Lambda Web Adapter for web applications, or Event Source Mappings for event-driven architectures. AWS handles infrastructure provisioning, scaling, and monitoring automatically.
Key capabilities:
Load the appropriate reference file based on what the user is working on:
sam_init or cdk init with an appropriate template for your use caseGlobals in SAM, construct props in CDK)secure_esm_* tools to generate correct IAM policies for event source mappings*) resource ARNs or actions in IAM policiesFor topic-specific best practices, see the dedicated guide files in the reference table above.
Limits that developers commonly hit:
| Resource | Limit |
|---|---|
| Function timeout | 900 seconds (15 minutes) |
| Memory | 128 MB – 10,240 MB |
| 1 vCPU equivalent | 1,769 MB memory |
| Synchronous payload (request + response) | 6 MB each |
| Async invocation payload | 1 MB |
| Streamed response | 200 MB |
| Deployment package (.zip, uncompressed) | 250 MB |
| Deployment package (.zip upload, compressed) | 50 MB |
| Container image | 10 GB |
| Layers per function | 5 |
| Environment variables (aggregate) | 4 KB |
/tmp ephemeral storage | 512 MB – 10,240 MB |
| Account concurrent executions (default) | 1,000 (requestable increase) |
| Burst scaling rate | 1,000 new executions per 10 seconds |
Check Service Quotas for your account limits: aws lambda get-account-settings
| Error | Cause | Solution |
|---|---|---|
Build Failed | Missing dependencies | Run sam_build with use_container: true |
Stack is in ROLLBACK_COMPLETE | Previous deploy failed | Delete stack with aws cloudformation delete-stack, redeploy |
IteratorAge increasing | Stream consumer falling behind | Increase ParallelizationFactor and BatchSize. Use esm_optimize |
| EventBridge events silently dropped | No DLQ, retries exhausted | Add RetryPolicy + DeadLetterConfig to rule target |
| Step Functions failing silently | No retry on Task state | Add Retry with Lambda.ServiceException, Lambda.AWSLambdaException |
| Durable Function not resuming | Missing IAM permissions | Add lambda:CheckpointDurableExecution and lambda:GetDurableExecutionState — see durable-functions skill |
For detailed troubleshooting, see references/troubleshooting.md.
This skill requires that AWS credentials are configured on the host machine:
Verify access: Run aws sts get-caller-identity to confirm credentials are valid
sam --versionsam_local_invoke and container-based buildsdocker --version or finch --versionWrite access is enabled by default. The plugin ships with --allow-write in .mcp.json, so the MCP server can create projects, generate IaC, and deploy on behalf of the user.
Access to sensitive data (like Lambda and API Gateway logs) is not enabled by default. To grant it, add --allow-sensitive-data-access to .mcp.json.
This plugin includes a PostToolUse hook that runs sam validate automatically after any edit to template.yaml or template.yml. If validation fails, the error is returned as a system message so you can fix it immediately. The hook requires SAM CLI and jq to be installed; if either is missing, validation is skipped with a system message. Users can disable it via /hooks.
Verify: Run jq --version
Default: TypeScript
Override syntax:
When not specified, ALWAYS use TypeScript
Default: CDK
Override syntax:
When not specified, ALWAYS use CDK