Tool use: what happens when agents call calculators, shells, and APIs
What do AI research papers actually find when models call external tools?
Tool use is what lets a model stop just talking and start acting: calling a search engine, running shell commands, querying a database, or invoking another program and folding the result back into its answer. The papers keep circling back to it because every extra capability is also an attack surface — tool descriptions, file outputs, and bug reports become vectors for injected instructions, and agents often can't tell a genuine tool result from a manipulated one. They agree tool access helps, sometimes letting small trained agents beat much larger models that merely have tools available. They disagree on how to manage that access safely, debating whether experience is best stored as reusable code tools or plain text, and how to assign the right subset of tools to each agent without opening new failure modes.
What tool use means
Tool use is the model’s ability to call external functions — a calculator, a search engine, a code interpreter, an API — and use the results in its response. It’s what turns a chat model into something that can actually act in the world.
The episodes (51)
Newest first. Each line is what that paper contributed to the question.
- The Tool Description Was the Attack: How Agents Leak Their Own Context
The attack exploits how agents select and populate arguments for external tools/functions in a tool-calling loop. (0 out of 200 malicious tools flagged)
- Stealing an AI Agent's Expertise Without Copying a Word of It
Hidden skills include tool preconditions and output schemas that agents invoke, which the attack tries (and fails) to recover exactly. (~87% of the capability gap closed in ~30 queries)
- The Same Model Refused a Backdoor, Then Its Own Sub-Agent Ran It
Attacker content enters via tool outputs like files and shell command results that the agent reads and acts on. (13 out of 13 on all six harnesses)
- Poisoned Bug Reports Fooled Coding Agents Two Times Out of Three
The agents' ability to run shell commands and install packages is exactly what the injected instructions exploit. (66.5% of attacks succeeded)
- The AI Agent That Found the Truth and Typed the Lie Anyway
The agent's search tool calls and when it decides to stop calling them is central to the failure mechanism. (96% to 26% from one fake page)
- The Bias Isn't in Your Prompt — It's Inside the Model
Coin-flip and timestamp randomness tools are used to test whether models cheat even 'fair' external randomness. (6.5 points lower on its own maker's bubble odds)
- Why an AI Called Fourteen Broken Figures Perfect, And What It Reveals About Test-Time Compute
Grounded instruments like linters, code execution, and geometry tools drive the interaction loop's fixes. (14 of 15 rated perfect, only 3 actually clean)
- The Blank Space in Your AI Approval Box That Isn't Empty
The attack exploits how MCP tool descriptions are fed into an AI assistant's context as trusted instructions. (1 of 8 attacks stayed fully invisible)
- How Do You Know an AI Agent Actually Refused? Check the World, Not the Words
A monitored tool gateway records real tool outputs versus what the agent is shown, central to detecting deception. (94%)
- Why 'Be Careful' Does Nothing for AI Coding Agents, and What Does
Coding agents with shell access execute destructive real-world actions based on vague natural-language instructions. (65.5% vs 64% action rate — sandbox vs production cues)
- How a Robot Builds a Debugging Notebook It Can Read, Edit, and Hand to Another Robot
Robot programs stitch together pre-built subroutines (perception, motion planning, grasping) as callable tools via code-as-policy. (31% vs 4%)
- A 32B Open Model Matched Frontier Systems By Learning to Take Notes
Memory operations (read, write, search, upsert) are elevated to first-class agent actions interleaved with task actions. (2x-4x gains, same weights)
- The Skill Every AI Manager Is Missing: Handing Out Exactly the Right Keys
A key management axis is whether the orchestrator assigns the right subset of tools to each helper agent. (under 50% permission precision)
- An 8-Billion Agent That Beats Models 80 Times Its Size By Looking Things Up
The paper's central finding is that training an agent to actively use medical tools beats larger models that merely have access to tools. (8B beats 671B by 15+ points)
- An AI Built an Undetectable Secret Channel, And Another AI Couldn't Find It
Tool access—web search, filesystem, a helper model for token probabilities—is what makes the construction barrier collapse.
- How to Backpropagate Blame Through a Team of Chatbots — And When It Backfires
The τ-bench retail task requires agents to make correct tool calls as part of evaluation. (71 to 7)
- One Crosscoder Feature Flips a Stalling Chatbot Into a Working Agent
Tool-calling accuracy is the target behavior the paper tries to localize, steer, and transfer via crosscoder features. (+65 percentage points from one feature)
- When a One-Liner Beats Your Agent's Clever Verification Logic
The paper models a menu of tools (syntax checker, test suite, LLM critic, oracle) with different costs and reliabilities. (670-second verification)
- Why Better Bug Reports Can Make AI Coding Agents Worse
SHERLOC uses a fixed four-tool menu (view file, search, repo tree, connected tree) as the agent's only interface to the codebase. (74% to 10%)
- When Turning Experience Into Code Makes Your AI Agent Dumber
A central comparison is between storing experience as callable code tools versus natural-language text, with tools shown to fail under distribution shift. (53% vs 63%)
- How Teaching an AI to Predict, Not Act, Made It a Better Actor
World-model warm-up with zero tool-calling data transferred to multi-turn tool-use benchmarks, improving performance by ~9 points on average. (9 points better on an unseen benchmark)
- A Robot That Plays Before You Give It a Job, And Why That Beats Retrying
The Code-as-Policy agent calls structured perception, grasping, and motion tools as building blocks of its generated programs.
- When an AI Coding Agent Drives a Phone Through the Terminal, No Screen Needed
Custom database-query and file-access tools are added to the terminal agent, and the paper studies how tool benefit varies with underlying model strength.
- Don't Kill the Loser: A Different Way to Handle Two AI Agents Colliding
The ToolSmith component dynamically generates footprint-declared, undoable tools for agents operating on bare systems.
- Agents Fail at the Body, Not the Brain: A Self-Rewriting Scaffold That Lifts a 9B Model 44 Points
The Wikipedia repair story exemplifies runtime tool generation: the system writes and deploys a new retrieval tool autonomously mid-run.
- When an AI Agent Just Copies Its Tool — And Bigger Models Copy More
The entire paper examines how LLM agents invoke and over-trust a GNN specialist tool for node classification.
- Training a Tiny Model to Run the Plumbing Between an Agent and the World
The harness operates on generic tool-use trajectories — intercepting and filtering shell commands and environment observations between the LLM and the real environment.
- Five Identical Worlds, One Swapped Model: What Happens When AI Agents Run for Fifteen Days
Agent capabilities are gated by location and preconditions at runtime, making certain tools literally uncallable rather than merely discouraged.
- How an AI Agent Rewrites Its Own Tools, Without an Answer Key
The optimized harness includes new executable scripts/tools the agent writes for itself, going beyond memory to actionable machinery.
- How an Agent Got 44 Points Better by Mining Its Own Scratch Paper
The paper introduces 'pseudo-tools' — LLM-backed callable tools with natural-language descriptions extracted from agent traces.
- The Reasoning Cliff: Why Thinking Longer Makes Models Worse at Exact Step-by-Step Tasks
The main prescription is to delegate past the 'deterministic horizon' to exact algorithmic tools rather than continuing to reason neurally.
- The Trojan Is Your Agent's Memory: Why Single-Step Defenses Miss Persistent Attacks
The agent harness gives models file read/write and shell access, which are the channels through which the attack plants and triggers backdoors.
- How Making a Research Agent Smarter Quietly Makes It Leak Your Secrets
The agents' primary mechanism is issuing queries to a search engine as an external tool, and the privacy risk arises directly from that tool-use pattern.
- How a Prompt Wrapper Lets a Frontier Model Play Poker Like an Expert
Deterministic code computes hard game-state facts (hand class, pot odds, stack depth) that are fed to the model, preventing hallucination.
- Same Tokens, Same Cost, Wildly Different Results: What Actually Scales in AI Agents
The metric scores tool-call results on validity and non-redundancy, making tool-use quality a first-class variable in the scaling framework.
- When AI-Written Papers Read Well But the Evidence Underneath Is Broken
DeepScientist was instructed to call the Semantic Scholar API for citation verification but never did, illustrating tool-use failures in agentic pipelines.
- An AI Just Solved a 1996 Erdős Problem—and the Simplest Agent Won
Agent B and D variants call AlphaProof as an external specialized tool for subgoal proving.
- Why Giving an AI Agent More Tools Can Make It Worse at Using a Computer
The central experiment is adding structured tool calls to a GUI agent's action space and studying the performance impact.
- Why Web Agents Are Slow: A Compiler-Style Fix for Computer-Use Latency
Cached browser tools with typed preconditions and postconditions are the building blocks of the compiled agent programs.
- Treating Hallucinations as Exploits: A Gate-Based Architecture for Agent Safety
The architecture centers on constraining which tool-invocation actions can be authorized based on certified evidence rather than model-generated claims.
- Firefly's Inversion: Building Verified Tool-Call Training Data by Working Backward
The paper focuses entirely on training models to make verified sequences of tool/API calls.
- How Uber Caught 206 Leaked Credentials With an LLM-Powered Security Stack
MCP-connected tool calls are the primary surface area for attacks ADR is designed to detect.
- Two Frozen Models Learn to Whisper: Coupling Through Hidden States
The auxiliary model has access to tools (calculator, Z3 solver, Python) and the architecture enables the primary to benefit from their results.
- When Smarter Agents Get Fooled by Three Extra Nodes in a Database
The vulnerability exploits the agent's trusted tool-call channel (MCP) to deliver poisoned structured data as observational ground truth.
- Why Frontier Agents Ask for Clarification at Exactly the Wrong Moment
Agents are evaluated on tool-use benchmarks and use an ask-the-user tool whose invocation timing is the central variable.
- Why Forty-Eight Percent on FrontierMath Isn't the Real Story in DeepMind's New Math Paper
The system uses coding agents to run Python (e.g., PySAT) and literature search tools as part of its problem-solving.
- An AI Agent That Found 28 Zero-Days in Windows — And What Made It Work
slyp uses three specialized tool servers (binary exploration, COM inspection, dynamic debugging) that the LLM calls to do grunt work.
- Ten Thousand Examples Beat the Full Industrial Pipeline for Search Agents
Expanding tool diversity in training demonstrations is one of the three core data modifications studied in the paper.
- The Compliance Gap: Why AI Says Yes and Does No
The gap is operationalized and measured through tool-call logs, making tool-use behavior the ground-truth channel for actual compliance versus verbal compliance.
- Why Your Coding Agent Stalls While the GPU Runs Hot
Tool calls create CPU load spikes and GPU idle periods that MARS must jointly schedule around, making tool-use patterns central to the problem.
- When RL Actually Teaches Agents Something New, And When It Doesn't
Agents use a search tool across multiple interaction rounds, making tool-use the key differentiator from pure math reasoning benchmarks.
Papers we have not covered yet
- Search-o1: Agentic Search-Enhanced Large Reasoning Models
- AgentDojo: A Dynamic Environment to Evaluate Attacks and Defenses for LLM Agents
- Not What You've Signed Up For: Compromising Real-World LLM-Integrated Applications with Indirect Prompt Injection
- ToolBench: Facilitating Large Language Models to Master 16000+ Real-world APIs
- τ-bench: A Benchmark for Tool-Agent-User Interaction in Real-World Domains
- AlphaProof and AlphaGeometry 2: AI achieves silver-medal standard solving International Mathematical Olympiad problems
- ReAct: Synergizing Reasoning and Acting in Language Models
- Scaling LLM Test-Time Compute Optimally Can be More Effective than Scaling Model Parameters
- Toolformer: Language Models Can Teach Themselves to Use Tools
- Graph Neural Networks: A Review of Methods and Applications
- AppAgent: Multimodal Agents as Smartphone Users
- Code as Policies: Language Model Programs for Embodied Control
Other guides
Intro written by Anthropic's Claude Sonnet 5; episodes selected and edited by Garrett Casey. Episode notes come from each episode's own analysis. How PaperDive is made.