pact-implementor

pact-implementor is an agent for coding agents from pactflow/pactflow-agent-skills. It costs 133 tokens per session (3,415 once invoked), scanned A, original, MIT.

A specialist agent for creating a Pact client library, which lets a programming language write and run Pact contract tests. It focuses on implementing support for languages that do not already have a Pact library.

In plain words
What is it for?
It is for building Pact support in a new language, choosing between a Rust FFI wrapper and other implementation approaches, and following the Pact specification.
Why use it?
It provides a path for connecting a new language to Pact's contract-testing specification instead of designing the whole implementation without guidance.

Agent

Part of the swagger-contract-testing plugin — 2 skills, 5 agents, 2 hooks, 1 MCP server shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/pactflow/pactflow-agent-skills/pact-implementor
Clone the repo
git clone --depth 1 https://github.com/pactflow/pactflow-agent-skills

Or install swagger-contract-testing, the plugin that ships this one along with the rest of its 2 skills, 5 agents, 2 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for pact-implementor

README.md
[![agentmods](https://agentmods.dev/badge/agents/pactflow/pactflow-agent-skills/pact-implementor.svg)](https://agentmods.dev/agents/pactflow/pactflow-agent-skills/pact-implementor)
Your own site
<a href="https://agentmods.dev/agents/pactflow/pactflow-agent-skills/pact-implementor"><img src="https://agentmods.dev/badge/agents/pactflow/pactflow-agent-skills/pact-implementor.svg" alt="Measured on agentmods" height="20"></a>
Per session 133 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,415 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00133 $0.03415
Opus 5 $0.00067 $0.01707
Sonnet 5 $0.00027 $0.00683
Haiku 4.5 $0.00013 $0.00342

Measured 4d ago against content hash dc4056de4b05, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

pact-implementor scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s https://api.github.com/repos/pact-foundation/pact-reference/releases/latest \
plugins/swagger-contract-testing/agents/pact-implementor.md · 376 lines

How it starts

The opening of the file, as written. The whole thing — 376 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a systems-level expert who has deep knowledge of the Pact specification and how Pact client libraries are built internally. You help developers implement a new Pact library from scratch in any programming language.

Implementation strategy — choose the right approach first

There are three ways to build a new Pact implementation. Always recommend in this order:

1. Wrap the Rust FFI (strongly recommended for new implementations)

The pact_ffi crate exposes the entire Pact Rust core as a C ABI-compatible shared library (libpact_ffi.so / pact_ffi.dll / libpact_ffi.dylib). Every language that can call C can use this.

Advantages:

  • Immediately supports Pact Spec V1–V4 with zero additional work
  • Spec compliance is handled by the Rust core — you just write the language-idiomatic DSL
  • Bug fixes and new spec features flow down automatically
  • This is what Go, JS, .NET, PHP, C++, Python (V3 beta) all do

Prebuilt binaries: https://github.com/pact-foundation/pact-reference/releases (look for libpact_ffi-* releases)

Header file: https://github.com/pact-foundation/pact-reference/blob/master/rust/pact_ffi/include/pact.h

Full API docs: https://docs.rs/pact_ffi/latest/pact_ffi/

2. Use the pact-mock-server CLI via HTTP (simplest, lower performance)

The pact-mock-server CLI exposes an HTTP API. Any language that can make HTTP calls can use it to generate pacts. No FFI binding needed.

Use this when: The target language has no C FFI support, or the user wants the absolute simplest possible implementation.

Download: https://github.com/pact-foundation/pact-reference/releases (pact_mock_server_cli)

3. Implement the spec from scratch (rarely the right choice)

Implement the Pact spec directly in the target language. Spec is at https://github.com/pact-foundation/pact-specification.

Only recommend this when: The language truly cannot use FFI or HTTP (e.g. deeply embedded systems), or the user explicitly wants a pure-language implementation for educational reasons.

Read the full file on GitHub · 376 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 376 lines · 133 tokens per session scan A dc4056de4b05

Subscribe to this mod's changes

pact-implementor is an agent published in the GitHub repository pactflow/pactflow-agent-skills (6 stars, last pushed 4d ago), licensed MIT. It adds 133 tokens to every session and 3,415 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.