// MCP TOOL REFERENCE

java_start

Start the Java Language Server (JDT.LS). Required before other commands. If already running, it will restart.

Accepts file system path (javaRuntimes[].path); High parameter count (11 properties)

Part of the Java Jdtls MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.

@sachiewonder/java-jdtls-mcp-server Execute Risk 4/5

// WHEN AI AGENTS USE THIS TOOL

AI agents invoke java_start to trigger processes or run actions in Java Jdtls. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.

// WHY ENFORCE A POLICY ON JAVA_START

java_start can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. Intercept enforces rate limits and validates arguments to keep execution within safe bounds.

// RECOMMENDED POLICY

Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.

java-jdtls.yaml

tools:
  java_start:
    rules:
      - action: allow
        rate_limit:
          max: 10
          window: 60
        validate:
          required_args: true

See the full Java Jdtls policy for all 15 tools.

// DETAILS

Tool Name java_start

Category Execute

MCP Server Java Jdtls MCP Server

Risk Level High

// MORE JAVA JDTLS TOOLS

Execute java_restart Write configure_jdt_ls Write java_open_file Read find_references Read java_get_definition Read java_get_diagnostics Read java_get_file_symbols Read java_get_hover

View all 15 tools →

// WHAT CAN GO WRONG

Agents calling execute-class tools like java_start have been implicated in these attack patterns. Read the full case and prevention policy for each:

Browse the full MCP Attack Database →

// OTHER EXECUTE TOOLS ACROSS MCP SERVERS

Other tools in the Execute risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.

Agent Passport System — Cryptographic Identity for AI Agents commerce_preflight Agent Passport System — Cryptographic Identity for AI Agents execute_with_context Agent Passport System — Cryptographic Identity for AI Agents gateway_execute_approval Agent Passport System — Cryptographic Identity for AI Agents governance_360 Agent Passport System — Cryptographic Identity for AI Agents parse_governance_block_html AgentClear — API Marketplace for AI Agents call_service

// IN CONTEXT OF HIGH RISK

java_start is one of the high-risk operations in Java Jdtls. For the full severity-focused view — only the high-risk tools with their recommended policies — see the breakdown for this server, or browse all high-risk tools across every MCP server.

// RELATED READING

// FAQ

What does the java_start tool do? +

Start the Java Language Server (JDT.LS). Required before other commands. If already running, it will restart.. It is categorised as a Execute tool in the Java Jdtls MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on java_start? +

Add a rule in your Intercept YAML policy under the tools section for java_start. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Java Jdtls MCP server.

What risk level is java_start? +

java_start is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit java_start? +

Yes. Add a rate_limit block to the java_start 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.

How do I block java_start completely? +

Set action: deny in the Intercept policy for java_start. 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.

What MCP server provides java_start? +

java_start is provided by the Java Jdtls MCP server (@sachiewonder/java-jdtls-mcp-server). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.

java_start

Enforce policies on Java Jdtls