Agent tools should be trustworthy.
We built FunctionFly so AI agents can call any function and know — not hope — that it's safe, signed, and behaving as advertised. Trust is technical, not metaphorical.
Every tool an agent calls
is a leap of faith
Today, AI agents call functions — email senders, payment processors, database queries — with no way to verify those functions do what they claim. There's no trust infrastructure: no verification, no attestations, no execution history, no trust scores.
Existing platforms treat tools as dumb endpoints. Define the API, the agent calls it, whatever comes back is accepted. But in a world where agents act autonomously on your behalf, that gap is not just a technical problem — it's a security and reliability crisis waiting to happen.
What happens when a function has a subtle bug? What happens when it's been compromised? What happens when an agent naively calls a function that has quietly changed behavior? Nobody knows — because there's no audit trail, no trust signal, no verification layer.
FunctionFly is the
trust layer
A complete trust infrastructure for AI agent tool usage — from publication to execution to trust score.
Publish & Verify
Publish a function with a manifest describing its behavior, capabilities, and intended use. Submit to automated verification — static analysis, fuzzing, signature checks — and human attestation for higher trust tiers.
Sandbox Execution
Every function call runs in an isolated WebAssembly sandbox with declared capabilities enforced at runtime. No filesystem access, no network egress, no privilege escalation — unless explicitly granted in the manifest.
Trust Scores
Every execution feeds into a live trust score. Functions that run successfully thousands of times earn higher scores. Functions that fail, time out, or behave unexpectedly are penalized. Agents can set policy thresholds and refuse to call functions below a given tier.
Zero-Knowledge Vault
Store API keys, secrets, and sensitive config in the FunctionFly Vault. Encryption and decryption happen client-side — the server never sees your plaintext or your passphrase. Your secrets never leave your control.
The principles behind
every decision
Deny-by-default capabilities
Every capability — network access, filesystem read/write, environment variable exposure — must be declared at publish time and is enforced at runtime by the sandbox. A function that hasn't declared network access cannot make outbound requests. No ambient authority, ever.
Trust is earned, not claimed
Trust scores are computed from real execution outcomes. A function that has run 50,000 times with a 99.97% success rate has a measurably different trust profile than one that's never been called. Agents can query trust scores before making calls, and operators can set minimum thresholds per policy.
Multi-level verification
Functions can submit to automated checks — static analysis, fuzzing, signature validation, sandbox behavior tests — and human attestation for higher trust tiers. Higher tiers unlock broader agent policies and higher call volume limits. Verification is ongoing, not one-time.
Observability is not optional
Every function call is recorded: input, output, latency, cost, trust score delta, and failure mode. Execution traces, audit logs, and metrics dashboards give operators complete visibility. If something goes wrong, you know exactly what happened and why — not just that it failed.
Multi-language, no rewrites
Write functions in Python, Go, Rust, JavaScript, or WebAssembly. One SDK, every runtime. Agents discover and call functions through a single registry interface — language is an implementation detail, not an integration burden. Switch languages without rewriting your tool integrations.
Zero-knowledge by design
Secrets in the FunctionFly Vault are encrypted client-side with a key derived from your passphrase. The server stores only ciphertext, IV, salt, and auth tag — it cannot decrypt your secrets and cannot perform key recovery. If you lose your passphrase, your secrets are unrecoverable. That's the point.
What we stand for
Six beliefs that shape every product decision, every architectural choice, and every line of code we ship.
Trust is technical
We don't sell trust as a feeling. We build measurable signals — verification levels, execution history, signed attestations, trust scores — that agents and operators can audit programmatically.
Safe by default
Every function runs with the minimum capabilities it needs — nothing more. No ambient authority, no implicit permissions, no "just trust us." The sandbox enforces this, not convention or good intentions.
Agent-native from day one
We didn't bolt trust onto an existing API gateway. FunctionFly was designed for agents to discover, evaluate, and call functions — with manifests, trust filters, capability declarations, and policy routing built in from the start.
Measurable, not magical
Trust tiers are earned through verifiable evidence — not self-attestation or marketing language. Automated tests, execution history, and human reviews are the inputs. Trust scores are the output.
Multi-language, no rewrites
Write in Python, Go, Rust, JavaScript, or WASM. One SDK, every runtime. Agents discover functions through a single registry regardless of the language they're written in — language is an implementation detail.
Full observability
Execution traces, audit logs, latency breakdowns, cost attribution, and trust score history. Every function call produces a complete record so operators can audit, debug, and improve their function ecosystem over time.
How we got here
Founded
FunctionFly incorporated in Wyoming, headquartered in Fort Worth, TX. Began building the trust layer for AI agents — focusing on verified execution, capability-based sandboxing, and auditable trust scores.
Beta Launch
Public beta launch with multi-language SDKs for Python, Go, Rust, and JavaScript. Released the function registry API for publication and discovery. Zero-knowledge Vault with client-side AES-256-GCM encryption.
Today
FunctionFly powers trust for agents across production deployments. 5 language runtimes, 4 trust tiers, 12 global regions, billions of function calls processed. We're just getting started.
Small team. Big ideas.
Engineers and designers who've spent years working on distributed systems, security, and developer tooling — now focused entirely on AI agent trust infrastructure.
Ready to build with
trust infrastructure?
Whether you're building agent tooling, evaluating trust infrastructure, or just want to understand how FunctionFly works — get started in minutes.
No credit card required. Free tier includes 10,000 function calls/month.