An AI co-GM for your Pathfinder 2e table

It knows it is not running D&D

Open Familiar on a Pathfinder world and the first reply already names Pathfinder Second Edition. There is no setting to find. It looks rules up in the compendium and journals in your own world rather than reciting something from memory, and it hands every adjudication back to you.

Asked how flanking works, it answered in Remaster vocabulary and named off-guard, out of the Conditions compendium in the world it was looking at. Not the legacy term, and not the D&D equivalent. Then it gave the geometry call back to the GM, which is where that call belongs.

The guard is in the very first request, before you have configured anything. A freshly enabled module on a fresh Pathfinder world behaves the same way.

Where the rules engine stops

Familiar is built deepest for D&D 5e (2024), where it referees the rules outright. On Pathfinder 2e it runs the half of the table that was never about rules, and it stays out of the half that is.

Refereeing the rules is D&D 5e (2024) only. In combat the tracker, the turns, and the tokens still work; the rulings stay yours.

One setting to change: turn the combat auto-pilot off in Familiar's settings. It drives NPC turns through the 5e engine, so it does not know your system.

Everything in this table was run on a real Pathfinder 2e world, not read off a spec.

Pathfinder keeps the math. Familiar takes the table.

This is the whole shape of it on Pathfinder 2e, and it is a better split than it sounds. Degrees of success, conditions, immunities and resistances, the encounter budget: your system already resolves all of that, and it was built by people who care about getting it exactly right. Familiar keeps its hands off.

What is left is everything the system was never trying to do. When it does reach for a creature or an item, it searches the Pathfinder packs installed in your own world, so the numbers on the sheet came from your compendium rather than from a model guessing at them.

• Scene, lighting, weather, and the ambient track, set from a sentence
• Every NPC voiced, with a want of their own and the nerve to refuse the party
• Journals written and read back, so the session leaves a record you can search
• Campaign memory that outlives the context window, kept in your world
• Creature and item lookup across the packs you actually have installed

The parts of a Pathfinder session that eat your evening

Not the rules. The rest of it. These are the jobs a Pathfinder GM does between the dice, and they are the jobs Familiar was built to take.

• A Recall Knowledge check lands and you need something true, useful, and immediate about a creature the party has never fought
• The encounter is built to budget, but the room it happens in is still a blank canvas
• Four NPCs in one market scene, each of whom needs to sound like a different person
• Someone asks what the merchant told them in the session before last, and your notes are forty pages long
• A creature nobody at the table has met needs describing before a single die has been rolled

What that looks like in one ask

"Set up a goblin ambush on this road, two of them, and give me the scene." What came back, on a real Pathfinder world: a search across that world's own packs, two Goblin Warriors imported out of Monster Core, both placed hostile on the map, and the road described well enough to read aloud.

The dice that follow are Pathfinder's. The initiative prompt is Pathfinder's. The ambush, the voices, and the scene are the part you did not have to prepare.

The starter your table begins from

Familiar carries a Table Rules field per world, under Settings, System Rules. Whatever you put there is appended to every request, and it reaches your MCP client too.

Pathfinder 2e has its own starter, offered first when Familiar sees your world. It is a starting point rather than a ruleset: the terms, the table culture, and slots for your setting, your tone, and your house rules. Paste it, then cut what does not match your table.

We play Pathfinder Second Edition (Remaster). Use Pathfinder terms: three-action economy, degrees of success, Hero Points, proficiency ranks, off-guard. Look rules up in this world's compendium and journals, and defer all rules adjudication to the GM.
Let the PF2e system resolve rolls, saves, conditions, and degrees of success.
Standing guidance:
- Read each roll as one of four degrees; narrate a critical success or failure as a real swing.
- Build to the encounter budget and let outcomes stand; the math is tuned, so do not soften a roll or pad a foe's health.
- When a character could not know if they succeeded, keep the result hidden and describe only what they sense.
- Play enemies to their tactics: use the whole turn, move for position, and set up flanks over trading single blows.
- When a character Recalls Knowledge, give something true and useful, with more on a critical success.
- Draw NPCs and lore from this world's journals, not memory, and say when something was never written down.
Setting: [Golarion region such as Absalom or the Mwangi Expanse, or your own world].
Tone: [heroic / gritty].
House rules:
- [rule one]
- [rule two]
Never speak or decide for the player characters.

Two things it will tell you it cannot do

Both are Pathfinder-shaped, and in both cases Familiar says so plainly rather than reporting success and doing nothing.

• Conditions are items in Pathfinder, not simple toggles, so Familiar cannot switch one on from chat. Ask it to and it says that, instead of quietly failing. You apply it on the sheet, the way you already do.
• Initiative opens Pathfinder's own roll prompt for each combatant and waits for you. That is the system's UI doing its job, and Familiar does not reach around it.

A wary GM should read this as the point rather than the catch. A tool that reaches into a well-automated system and starts overwriting its results is the thing you would actually have to worry about.

The parts that are the same everywhere

Connecting an AI, choosing a model, and what it costs do not change with your game system, so they are not repeated here.

• Everything Familiar can doThe full tool reference. Everything outside combat refereeing runs here too.
• Connect Claude, ChatGPT, or GeminiThe connection steps, identical on every game system.
• Choosing an AI modelWhich model, and how much thinking headroom a hard scene needs.