JMeter HITL (Human-in-the-Loop) Editing

When to Use This Skill

• User wants to analyze the structure of a JMeter JMX script
• User wants to add components (extractors, assertions, timers, etc.) to a JMX script
• User wants to edit existing components (rename, set properties, replace values)
• User wants to import an external JMX script into the artifacts folder
• User wants to run a headless JMeter smoke test to validate a script

Reference

This section provides context for humans and capable models. For the step-by-step execution instructions, skip to the Execution section below.

How HITL Editing Works

The HITL tools work on any valid JMX script, regardless of how it was created:

• JMeter GUI, BlazeMeter export, third-party tool, CI/CD pipeline
• Generated by mcp-perf-suite (Playwright, HAR, or Swagger workflows)

The workflow is interactive and user-directed, not a fixed linear pipeline. The user tells the agent what to analyze, add, or edit. The agent executes using the HITL MCP tools.

Script Sources

A JMX script can arrive in the artifacts folder from any of these sources:

• External / Pre-existing JMX — User provides a path to an existing JMX file. Copy it into artifacts/{test_run_id}/jmeter/ with an imported_ prefix.
• Playwright browser automation — Follow the skill at .cursor/skills/playwright-browser-automation/SKILL.md.
• HAR file conversion — Follow the skill at .cursor/skills/jmeter-har-conversion/SKILL.md.
• Swagger/OpenAPI conversion — Follow the skill at .cursor/skills/jmeter-swagger-conversion/SKILL.md.

Tool Reference

Edit Operations

The edit_jmeter_component tool supports these operations:

• {"op": "rename", "value": "New Name"} — Rename a component
• {"op": "set_prop", "name": "property_name", "value": "new_value"} — Set a property
• {"op": "replace_in_body", "old": "find_this", "new": "replace_with"} — Replace text in body
• {"op": "toggle_enabled"} — Enable or disable a component

Common HITL Patterns

Add assertions to all samplers:

1. Analyze script to get all HTTPSamplerProxy node_ids
2. For each sampler, add a response_assertion checking for status 200

Parameterize hardcoded values:

1. Analyze with detail_level="full" to see element properties
2. Check variables.undefined for missing variable definitions
3. Use edit_jmeter_component with replace_in_body to swap hardcoded values
4. Add a csv_dataset or user_defined_variables component to define new variables

Add think time between steps:

1. Analyze to get controller node_ids
2. Add constant_timer or flow_control_action as last child of each controller

Related Rules

• prerequisites.mdc — test_run_id and artifact structure validation
• skill-execution-rules.mdc — Follow steps in order, collect inputs first
• mcp-error-handling.mdc — MCP tool error handling (retry policy, reporting)
• jmeter-script-guardrails.mdc — Smoke test = 1/1/1, dry run first, analyze before edit

Execution Output Files

After headless execution, these files are written to artifacts/{test_run_id}/jmeter/:

Execution

This is an interactive workflow. The user directs what to analyze, add, or edit. Follow the phases below, but Steps 3-4 repeat as many times as the user needs.

Collect Inputs

Ask the user for the following values. Do not proceed until all required values are collected.

REQUIRED:
  test_run_id = [ask user]

CONDITIONAL:
  jmx_source  = [one of: "external", "already exists", "generate from HAR/Swagger/Playwright"]
  jmx_path    = [required if jmx_source is "external" — full path to the JMX file]

Step 1 — Import External JMX (if needed)

When: Only if the user is importing an external JMX file not already in the artifacts folder.

Input: test_run_id, jmx_path

Action:

1. Create directory artifacts/{test_run_id}/jmeter/ if it does not exist
2. Copy (do NOT move) the JMX file to artifacts/{test_run_id}/jmeter/imported_{filename}.jmx

Save: jmx_filename = imported_{filename}.jmx

Skip this step if the JMX already exists in the artifacts folder.

Step 2 — Analyze the Script

Input: test_run_id, jmx_filename (optional — auto-discovers if not provided)

Action: Call MCP tool analyze_jmeter_script

analyze_jmeter_script(
  test_run_id  = {test_run_id},
  jmx_filename = {jmx_filename},
  detail_level = "detailed"
)

Expected MCP response (summary only):

{
  "status": "OK",
  "test_run_id": "{test_run_id}",
  "jmx_path": "artifacts/{test_run_id}/jmeter/...",
  "jmx_filename": "...",
  "summary": { "total_elements": 142, "by_type": { "..." } },
  "outline": "- [ThreadGroup] TC01_Thread_Group  (id: a1b2c3d4e5)\n  ...",
  "exported_files": {
    "json": "artifacts/{test_run_id}/jmeter/analysis/jmx_structure_<timestamp>.json",
    "markdown": "artifacts/{test_run_id}/jmeter/analysis/jmx_structure_<timestamp>.md"
  }
}

Important: The MCP response does NOT include the full hierarchy, node_index, or variables. These are in the exported JSON file on disk.

Save from the MCP response: exported_files, outline, summary.

Read the exported JSON file at exported_files.json to obtain:

• node_index — all components with their node_id values (needed for add/edit)
• hierarchy — the nested script structure
• variables — defined, used, and undefined variables

On error: If status is "ERROR", stop. Report the error to the user.

Present the outline and key findings to the user. Ask what they want to add or edit.

Step 3 — Add or Edit Components (user-directed, repeatable)

This step repeats as many times as the user needs. Each cycle follows the same pattern.

To Add a Component:

Input: test_run_id, parent_node_id (from Step 2), user's request

Action: First, preview with dry run:

add_jmeter_component(
  test_run_id    = {test_run_id},
  component_type = {type from user request or list_jmeter_component_types},
  parent_node_id = {parent_node_id},
  component_config = {config based on user request},
  position       = "last",
  dry_run        = true
)

Review the dry run output with the user. If approved, apply:

add_jmeter_component(
  ...same parameters...,
  dry_run = false
)

To Edit a Component:

Input: test_run_id, target_node_id (from Step 2), user's request

Action: First, preview with dry run:

edit_jmeter_component(
  test_run_id    = {test_run_id},
  target_node_id = {target_node_id},
  operations     = [ {"op": "...", ...} ],
  dry_run        = true
)

Review the dry run output with the user. If approved, apply:

edit_jmeter_component(
  ...same parameters...,
  dry_run = false
)

After every applied change: Go to Step 4 to re-analyze.

Step 4 — Re-Analyze After Edits

Input: test_run_id

Action: Call MCP tool analyze_jmeter_script to refresh the persisted structure files with the latest node_ids after edits.

analyze_jmeter_script(
  test_run_id  = {test_run_id},
  detail_level = "detailed"
)

Verify the script structure is correct after the edit using the outline and summary from the response.

Save: exported_files (refreshed structure files). Read the new exported JSON file at exported_files.json to get the updated node_index — node IDs may have changed after edits.

Ask the user: "Do you want to make more changes?" — If yes, go back to Step 3.

Step 5 — Headless Smoke Test (optional)

When: Only if the user wants to run the script locally to validate it.

Critical: Smoke tests MUST use 1 thread, 1 second ramp-up, 1 loop. If the Thread Group has higher values, override to 1/1/1 before running.

5a. List Scripts

list_jmeter_scripts(
  test_run_id = {test_run_id}
)

Save: jmx_path from the scripts list.

5b. Start Test

start_jmeter_test(
  test_run_id = {test_run_id},
  jmx_path    = {jmx_path}
)

Save: pid from the response.

5c. Monitor Until Complete

Poll get_jmeter_run_status every few seconds until the test finishes:

get_jmeter_run_status(
  test_run_id = {test_run_id},
  pid         = {pid}
)

5d. Generate Report

generate_aggregate_report(
  test_run_id = {test_run_id}
)

Present the results to the user. If errors are found and the user wants to debug, follow the debugging skill at .cursor/skills/jmeter-debugging/SKILL.md.

Step 6 — Downstream Analysis (optional)

When: Only if the user wants to analyze test results with PerfAnalysis.

analyze_test_results(
  test_run_id = {test_run_id}
)

The PerfAnalysis MCP will find test-results.csv in the jmeter/ folder.

Error Handling

These rules apply to every step:

• Always analyze the script before any add/edit operation.
• Always use dry_run=true first, then dry_run=false to apply.
• If any MCP tool returns an error status, stop and report to the user.
• Do NOT write code to fix MCP tool issues.
• Advise the user to close JMeter GUI during HITL edits to prevent file conflicts.