check-dev

A command for type-checking a Z specification with fuzz, a tool that checks whether the mathematical notation is written consistently. A Z specification is a precise description of a system's state and operations.

In plain words
What is it for?
Use it to check a chosen Z file or one found in the docs folder, then review reported errors and readiness warnings.
Why use it?
It finds notation and type errors before you try to analyse or animate the model, and can warn about patterns that later cause animation failures.

Command

Part of the z-spec-dev plugin — 42 commands, 1 hook 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 commands/punt-labs/z-spec/check-dev
Clone the repo
git clone --depth 1 https://github.com/punt-labs/z-spec

Or install z-spec-dev, the plugin that ships this one along with the rest of its 42 commands, 1 hook.

Per session 7 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,035 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00007 $0.01035
Opus 5 $0.00003 $0.00517
Sonnet 5 $0.00001 $0.00207
Haiku 4.5 $0.00001 $0.00103

Measured 3d ago against content hash e26c51ba24a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

check-dev scanned grade A with 0 findings 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 3d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • check — 92% identical, 4 lines differ
plugin/commands/check-dev.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Check Z Specification with Fuzz

Type-check a Z specification using the fuzz type-checker.

Input

File: $ARGUMENTS

Process

1. Locate the Specification

If a file path is provided, use it directly.

If no file specified:

  • Look in docs/ for .tex files containing Z specifications
  • Present options if multiple files exist

2. Type-check

Call mcp__plugin_z-spec-dev_zspec__check with file set to the resolved path.

3. Report

The tool returns an object with ok (bool) and errors (list).

If the returned JSON has an error field (e.g. the binary is not installed), show that message to the user and stop — do not render the normal result.

  • ok: truefuzz: <name> OK.
  • ok: falsefuzz: <name> FAIL, then one line per error, indented two spaces: <line>:<column>: <message>.

The tool has written <stem>.fuzz.json; the show tool renders it in the Fuzz tab.

4. Animation Readiness Warnings

After a successful fuzz type-check, scan the specification for patterns that pass fuzz but cause probcli animation failures. For each pattern found, emit a warning. Only emit warnings that actually apply to the spec.

Checklist (prefix each with "Animation hint:"):

  • Unbounded \finset or \pfun: Any \finset X or X \pfun Y where X is a given set (declared with [X] syntax, not a free type declared with Type ::= ...) and there is no cardinality bound — either a direct \# variable \leq maxBound constraint or a domain subset constraint like \dom variable \subseteq boundedSet where boundedSet itself has a cardinality bound. Free types are already finite and do not need cardinality bounds. Fix: add an axdef constant and a cardinality constraint, or constrain the domain to a bounded set.

  • Cross products for records: Any \cross used to combine 3+ types (e.g., X \cross Y \cross Z) where a named schema with fields would be more appropriate. Fix: define a schema with named fields instead.

  • Bare-type quantifiers: Any \forall or \exists that quantifies over a given type directly (e.g., \forall n : NAME) instead of over a set from state (e.g., \forall n : members). Fix: scope the quantifier to the relevant state set.

Read the full file on GitHub · 81 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. 3d ago First seen · 81 lines · 7 tokens per session scan A e26c51ba24a5

Subscribe to this mod's changes

check-dev is a command published in the GitHub repository punt-labs/z-spec (5 stars, last pushed 3d ago), licensed MIT. It adds 7 tokens to every session and 1,035 once invoked, about $0.0000 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.