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Google ADK Quick Reference

Purpose: Fast API reference and common patterns for Google Agent Development Kit Target: Developers actively coding with ADK in Clojure

🎯 Quick Start

;; Most common operations - copy-paste ready

;; 1. Create basic LLM agent
(def agent
  (-> (LLMAgent/builder)
      (.setModel gemini-model)
      (.setSystemPrompt "You are helpful")
      (.build)))

;; 2. Execute agent
(def result (.execute agent "user input"))

;; 3. Get response text
(.getText result)

;; 4. Create simple tool
(def tool
  (-> (FunctionTool/builder)
      (.setName "tool_name")
      (.setDescription "What it does")
      (.setFunction
        (reify Function
          (apply [_ input]
            {"result" (process input)})))
      (.build)))

;; 5. Add tool to agent
(-> (LLMAgent/builder)
    (.setModel model)
    (.addTools [tool])
    (.build))

📚 Complete Reference

Imports

;; Core agent types
(import '[com.google.adk.agent LLMAgent
                               SequentialAgent
                               ParallelAgent
                               LoopAgent])

;; Model providers
(import '[com.google.adk.model GeminiModel
                               OpenAIModel])

;; Tool system
(import '[com.google.adk.tool FunctionTool
                              Tool])

;; Java utilities for callbacks
(import '[java.util.function Function
                            Predicate
                            Consumer])

;; REPL test:
;; (LLMAgent/builder) => should not error

Agent Creation

Basic LLM Agent:

(def agent
  (-> (LLMAgent/builder)
      (.setModel model)
      (.addTools tools)
      (.setSystemPrompt "You are helpful")
      (.build)))

;; REPL test:
;; (type agent) => com.google.adk.agent.LLMAgent

Complete LLM Agent (all options):

(def agent
  (-> (LLMAgent/builder)
      (.setModel gemini-model)
      (.addTools [tool1 tool2 tool3])
      (.setSystemPrompt "Detailed instructions...")
      (.setTemperature 0.7)        ; Creativity level
      (.setMaxTokens 2048)         ; Response length limit
      (.build)))

;; See also: cva-quickref-adk#temperature-guide
;; REPL test:
;; (.getModel agent) => GeminiModel instance
;; (.getTools agent) => [tool1 tool2 tool3]

Sequential Agent (pipeline):

(def seq-agent
  (-> (SequentialAgent/builder)
      (.addStep agent1)            ; Runs first
      (.addStep agent2)            ; Gets agent1 output
      (.addStep agent3)            ; Gets agent2 output
      (.build)))

;; REPL test:
;; (.execute seq-agent "input") => final agent3 output
;; See also: cva-patterns-sequential

Parallel Agent (concurrent execution):

(def par-agent
  (-> (ParallelAgent/builder)
      (.addAgent agent1)           ; All run simultaneously
      (.addAgent agent2)
      (.setAggregationStrategy :merge)  ; How to combine results
      (.build)))

;; REPL test:
;; (.execute par-agent "input") => merged results
;; See also: cva-patterns-parallel

Loop Agent (iterative):

(def loop-agent
  (-> (LoopAgent/builder)
      (.setAgent base-agent)
      (.setMaxIterations 5)        ; Safety limit
      (.setTerminationCondition
        (reify Predicate
          (test [_ result]
            (success? result))))   ; Custom success check
      (.build)))

;; REPL test:
;; (.execute loop-agent "solve step by step") => iterates until success
;; See also: cva-patterns-loop, cva-concepts-agent-types

Model Configuration

Gemini Model:

(def gemini-model
  (-> (GeminiModel/builder)
      (.setProjectId "your-project-id")
      (.setLocation "us-central1")
      (.setModelName "gemini-1.5-pro")
      (.setTemperature 0.7)
      (.setMaxOutputTokens 2048)
      (.setTopP 0.9)
      (.build)))

;; REPL test:
;; (type gemini-model) => com.google.adk.model.GeminiModel
;; See also: cva-setup-vertex#authentication

Temperature Presets:

;; Deterministic (factual, consistent)
{:temperature 0.0 :top-p 1.0}    ; Same output every time

;; Consistent (slight variation)
{:temperature 0.3 :top-p 0.8}    ; Good for classification

;; Balanced (default)
{:temperature 0.7 :top-p 0.9}    ; General purpose

;; Creative (varied output)
{:temperature 0.9 :top-p 0.95}   ; Brainstorming

;; Very creative (unpredictable)
{:temperature 1.0 :top-p 1.0}    ; Experimental

;; REPL test:
;; (-> (GeminiModel/builder)
;;     (.setTemperature 0.0)
;;     (.build))

Tool Building

Simple Function Tool:

(def tool
  (-> (FunctionTool/builder)
      (.setName "tool_name")
      (.setDescription "What it does")  ; LLM sees this
      (.setFunction
        (reify Function
          (apply [_ input]
            {"result" (process input)})))
      (.build)))

;; REPL test:
;; (.getName tool) => "tool_name"
;; (.apply (.getFunction tool) "test") => {"result" ...}

Tool with Input Schema:

(def calculator-tool
  (-> (FunctionTool/builder)
      (.setName "calculator")
      (.setDescription "Calculates math expressions")
      (.setInputSchema
        {"type" "object"
         "properties" {"expression" {"type" "string"}}
         "required" ["expression"]})  ; LLM must provide this
      (.setFunction
        (reify Function
          (apply [_ input]
            {"result" (eval-expr (get input "expression"))})))
      (.build)))

;; REPL test:
;; (.apply (.getFunction calculator-tool)
;;         {"expression" "2+2"}) => {"result" 4}

Agent as Tool (composition):

(defn agent->tool
  "Wrap an agent as a tool for use in other agents"
  [agent name description]
  (-> (FunctionTool/builder)
      (.setName name)
      (.setDescription description)
      (.setFunction
        (reify Function
          (apply [_ input]
            (.execute agent input))))
      (.build)))

;; Usage:
(def specialist-tool
  (agent->tool specialist-agent
               "python_expert"
               "Expert in Python programming"))

;; REPL test:
;; (.getName specialist-tool) => "python_expert"
;; See also: cva-patterns-agent-composition

Agent Execution

Simple Execution:

(def result (.execute agent "user input"))

;; REPL test:
;; (.getText result) => "agent response..."

With Runtime Configuration:

(def result
  (.execute agent
            "user input"
            {:max-tokens 1024        ; Override default
             :temperature 0.5}))     ; Override default

;; REPL test:
;; Useful for per-request customization

Streaming (real-time output):

(def stream (.executeStream agent "input"))

(doseq [chunk stream]
  (println (.getText chunk)))

;; REPL test:
;; Watch output appear incrementally
;; See also: cva-patterns-streaming

With Callback (async pattern):

(.execute agent
          "input"
          (reify Consumer
            (accept [_ result]
              (println "Result:" result))))

;; REPL test:
;; Callback fires when complete
;; See also: cva-patterns-async

Result Processing

Access Response Data:

;; Get text output
(.getText result)                    ; => "agent response..."

;; Get tool calls made by agent
(.getToolCalls result)               ; => [ToolCall(...), ...]

;; Get metadata
(.getMetadata result)                ; => {"finish_reason" "STOP", ...}

;; Get usage statistics
(.getUsage result)                   ; => Usage object
(.getTotalTokens (.getUsage result)) ; => 150

;; REPL test:
;; (keys (bean result)) => shows all available methods

Extract to Clojure Map:

(defn extract-response
  "Convert Java result to Clojure data"
  [result]
  {:text (.getText result)
   :tools (vec (.getToolCalls result))
   :tokens (.getTotalTokens (.getUsage result))
   :finish-reason (get (.getMetadata result) "finish_reason")})

;; REPL test:
;; (extract-response result) => {:text "..." :tools [...] ...}

💡 Common Patterns

Retry Pattern (exponential backoff)

(defn execute-with-retry
  "Retry agent execution with exponential backoff"
  [agent input max-retries]
  (loop [n 0]
    (try
      (.execute agent input)
      (catch Exception e
        (if (< n max-retries)
          (do
            (Thread/sleep (* 1000 (Math/pow 2 n)))  ; 1s, 2s, 4s, ...
            (recur (inc n)))
          (throw e))))))

;; REPL test:
;; (execute-with-retry agent "test" 3)
;; See also: cva-patterns-resilience

Fallback Pattern (multi-model)

(defn execute-with-fallback
  "Try primary agent, fall back to secondary on failure"
  [primary-agent fallback-agent input]
  (try
    (.execute primary-agent input)
    (catch Exception e
      (println "Primary failed, using fallback")
      (.execute fallback-agent input))))

;; REPL test:
;; (execute-with-fallback expensive-agent cheap-agent "test")
;; See also: cva-patterns-fallback

Chain Pattern (sequential processing)

(defn chain-agents
  "Pass output of each agent to the next"
  [agents input]
  (reduce (fn [acc agent]
            (.execute agent (:text acc)))
          {:text input}
          agents))

;; REPL test:
;; (chain-agents [analyzer summarizer translator] "data")
;; See also: cva-patterns-sequential

Router Pattern (intent-based)

(defn route-to-agent
  "Select agent based on input classification"
  [input agents]
  (let [intent (classify-intent input)  ; Your classification logic
        agent (get agents intent)]
    (.execute agent input)))

;; Usage:
(route-to-agent
  "What's the weather?"
  {:weather weather-agent
   :news news-agent
   :chat chat-agent})

;; REPL test:
;; Create classifier function first
;; See also: cva-patterns-routing

System Prompt Templates

;; General assistant
"You are a helpful assistant."

;; Domain expert
"You are an expert in [domain]. Answer concisely and accurately.
Cite sources when possible."

;; Tool-using agent
"You have access to these tools: [list].
Use them when appropriate to answer user questions.
Always explain which tool you used and why."

;; Structured output
"Answer in JSON format: {\"answer\": \"...\", \"confidence\": 0-1}
Be concise but accurate."

;; Multi-step reasoning
"Think step by step. Show your reasoning process.
Use tools to verify information."

;; REPL test:
;; (-> (LLMAgent/builder)
;;     (.setSystemPrompt "You are...")
;;     (.build))

Error Handling

Catch Specific Exceptions:

(try
  (.execute agent input)
  (catch com.google.adk.exceptions.RateLimitException e
    (println "Rate limit hit, waiting...")
    (Thread/sleep 60000)  ; Wait 1 minute
    (.execute agent input))
  (catch com.google.adk.exceptions.InvalidRequestException e
    (println "Invalid request:" (.getMessage e)))
  (catch Exception e
    (println "General error:" (.getMessage e))))

;; REPL test:
;; Trigger errors intentionally to test handling
;; See also: cva-patterns-error-handling

Safe Execute Wrapper:

(defn safe-execute
  "Execute agent and return success/error map"
  [agent input]
  (try
    {:success true
     :result (.execute agent input)}
    (catch Exception e
      {:success false
       :error (.getMessage e)
       :type (type e)})))

;; REPL test:
;; (safe-execute agent "test") => {:success true :result ...}

Logging & Debugging

Basic Logging:

(.setLogger agent
  (reify com.google.adk.observability.Logger
    (log [_ level message]
      (println (str "[" level "] " message)))))

;; REPL test:
;; Execute agent and watch log output

Tool Call Logging:

(defn log-tool-calls
  "Debug which tools were called and with what input"
  [result]
  (doseq [tool-call (.getToolCalls result)]
    (println "Tool:" (.getToolName tool-call))
    (println "Input:" (.getInput tool-call))
    (println "Output:" (.getOutput tool-call))))

;; REPL test:
;; (log-tool-calls result)

REPL Debug Helpers:

(comment
  ;; Inspect agent
  (type agent)                        ; => LLMAgent
  (.getModel agent)                   ; => GeminiModel
  (.getTools agent)                   ; => [tool1, tool2]

  ;; Inspect result
  (def r (.execute agent "test"))
  (.getText r)                        ; => response text
  (.getToolCalls r)                   ; => tool calls made
  (.getUsage r)                       ; => token usage

  ;; Inspect tool
  (.getName tool)                     ; => "tool_name"
  (.getDescription tool)              ; => description
  (.apply (.getFunction tool) "test") ; => test output
  )

🔧 Performance Tips

;; 1. Reuse agents (thread-safe, stateless)
(defonce agent (create-agent))

;; 2. Lazy load heavy resources
(defonce model
  (delay
    (-> (GeminiModel/builder)
        (.setProjectId "project")
        (.build))))

;; 3. Cache deterministic results
(def cached-execute
  (memoize
    (fn [input]
      (.execute agent input))))

;; 4. Batch requests for efficiency
(defn batch-execute
  [agent inputs]
  (mapv #(.execute agent %) inputs))

;; 5. Use streaming for long responses
(defn stream-execute [agent input]
  (.executeStream agent input))

;; REPL test:
;; (time (batch-execute agent ["a" "b" "c"]))
;; See also: cva-patterns-performance

🔄 Data Conversions

Java ↔ Clojure:

;; Java List → Clojure vector
(vec java-list)

;; Java Map → Clojure map
(into {} java-map)

;; Java Optional → Clojure value/nil
(.orElse java-optional nil)

;; Clojure vector → Java List
(java.util.ArrayList. clj-vec)

;; Clojure map → Java HashMap
(java.util.HashMap. clj-map)

;; Clojure nil → Java Optional
(java.util.Optional/ofNullable value)

;; REPL test:
;; (vec (java.util.ArrayList. [1 2 3])) => [1 2 3]
;; See also: cva-quickref-libpython for Python conversions

🔗 Related Skills

• cva-overview - High-level ADK concepts
• cva-concepts-agent-types - Agent type details
• cva-setup-vertex - Vertex AI setup
• cva-quickref-libpython - Python interop reference

📘 Official Documentation

• ADK Documentation: https://google.github.io/adk-docs/
• API Reference: https://google.github.io/adk-docs/api-reference/
• Examples: https://github.com/google/adk-examples
• Vertex AI Docs: https://cloud.google.com/vertex-ai/docs