---
name: postel
description: "Be conservative in what you send, liberal in what you accept."
license: MIT
tier: 1
allowed-tools:
  - read_file
  - write_file
related: [yaml-jazz, robust-first, empathic-expressions, empathic-templates, honest-forget, coherence-engine, sniffable-python]
tags: [moollm, robustness, interpretation, protocol, rfc]
---

# POSTEL — The Robustness Principle

> *"Be conservative in what you send, liberal in what you accept."*
> — Jon Postel, RFC 761 (1980)

---

## What Is It?

**POSTEL** is how MOOLLM handles ambiguity, errors, and incomplete instructions:

Instead of failing, **find the best possible interpretation** that:
1. Accomplishes the likely intent
2. Respects stated constraints
3. Preserves user autonomy
4. Fails gracefully if truly impossible

**Also known as:**
- The Robustness Principle
- Postel's Law
- Best Possible Interpretation Protocol
- Charitable Interpretation
- Be liberal in what you accept

---

## The Protocol

When faced with ambiguity:

```
1. GATHER context — what do we know?
2. INFER intent — what did they probably mean?
3. PROPOSE interpretation — state your understanding
4. ACT constructively — do the reasonable thing
5. REPORT uncertainty — flag what you assumed
```

---

## Examples

### Ambiguous Command

**Input:** `"delete the old files"`

**POSTEL Response:**
```
I interpret "old files" as files not modified in 30+ days.
Found 12 candidates in ./temp/

Before deleting, I'll:
1. List them for your review
2. Move to trash (not permanent delete)
3. Wait for confirmation

Proceed? [Y/n]
```

### Incomplete Data

**Input:** User config missing email field

**POSTEL Response:**
```yaml
user:
  name: Alice
  email: null  # POSTEL: not provided, leaving empty
               # Will prompt if needed for notifications
```

### Contradictory Instructions

**Input:** "Make it faster AND more thorough"

**POSTEL Response:**
```
These goals tension against each other. 
Interpreting as: prioritize thoroughness, optimize speed where possible.

Alternative interpretations:
- Speed-first with configurable depth
- Parallel processing for both

Which approach fits your needs?
```

---

## Core Principles

### Jon Postel's Original Formulation

> *"Be conservative in what you send, liberal in what you accept."*

This was written for TCP implementations, but applies universally:
- **Accept messy input** — tolerate variations, typos, missing fields
- **Produce clean output** — be precise, complete, well-formed
- **Bridge the gap** — with charitable interpretation

### Charity

> *"Interpret others' words in the best possible light."*

Don't assume incompetence. Don't assume malice. Assume the human had good reasons you might not see.

### Transparency

Always **show your work**:
- State what you assumed
- Explain your interpretation  
- Offer alternatives
- Flag uncertainty

---

## When to Invoke

Use POSTEL when:
- Instructions are ambiguous
- Data is incomplete
- Commands seem contradictory
- Errors could be typos
- Context suggests different intent than literal reading

---

## Anti-Patterns

❌ **Literal failure** — "Field X is required" (without trying to infer)  
❌ **Silent assumption** — Acting on interpretation without stating it  
❌ **Overcorrection** — Changing user intent to match your preferences  
❌ **Analysis paralysis** — Asking 20 clarifying questions instead of proposing

---

## Jon Postel (1943-1998)

Jon Postel was one of the founding architects of the Internet. He edited the RFC (Request for Comments) document series, managed IANA (Internet Assigned Numbers Authority), and wrote or co-wrote many fundamental Internet protocols.

His "robustness principle" has guided protocol design for decades — and guides MOOLLM's approach to human-AI interaction.

---

## Dovetails With

### Sister Skills
- [yaml-jazz/](../yaml-jazz/) — Semantic interpretation
- [robust-first/](../robust-first/) — Survivability over correctness
- [self-repair/](../self-repair/) — POSTEL for error recovery

### Kernel
- [kernel/constitution-core.md](../../kernel/constitution-core.md) — Section 5: The Robustness Principle

---

## Protocol Symbol

```
POSTEL
```

Invoke when: Facing ambiguity. Choosing constructive action over failure.

Related symbols: `CHARITY`, `ROBUST-FIRST`

See: [PROTOCOLS.yml](../../PROTOCOLS.yml)