sema-usage

sema-usage is a skill for Claude Code from emergent-wisdom/sema. It costs 39 tokens per session (3,067 once invoked), scanned A, original, MIT.

A guide to Sema, a shared vocabulary system where each concept has a definition-based cryptographic name.

In plain words
What is it for?
Use it to search for vocabulary patterns, read their definitions, create new entries, verify meanings, and browse the vocabulary visually.
Why use it?
It helps agents find and reuse precise terms instead of repeatedly explaining the same concept, while allowing them to verify that a term has the intended meaning.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the sema plugin — 4 skills, 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 skills/emergent-wisdom/sema/sema-usage
Any agent
npx skills add emergent-wisdom/sema --skill sema-usage
Clone the repo
git clone --depth 1 https://github.com/emergent-wisdom/sema

Made for: Claude Code.

Or install sema, the plugin that ships this one along with the rest of its 4 skills, 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 sema-usage

README.md
[![agentmods](https://agentmods.dev/badge/skills/emergent-wisdom/sema/sema-usage.svg)](https://agentmods.dev/skills/emergent-wisdom/sema/sema-usage)
Your own site
<a href="https://agentmods.dev/skills/emergent-wisdom/sema/sema-usage"><img src="https://agentmods.dev/badge/skills/emergent-wisdom/sema/sema-usage.svg" alt="Measured on agentmods" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,067 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 5.1 $0.00039 $0.03067
Opus 5 $0.00019 $0.01533
Sonnet 5 $0.00008 $0.00613
Haiku 4.5 $0.00004 $0.00307

Measured 6d ago against content hash 95975566c5fe, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

sema-usage 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 6d 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.

skills/sema-usage/SKILL.md · 237 lines

How it starts

The opening of the file, as written. The whole thing — 237 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Speak in Sema

Sema is a content-addressed vocabulary protocol. ~450 patterns that give you precise, shared words for concepts that would otherwise require paragraphs of re-explanation. Each pattern has a handle (e.g. StateLock#c9c2) that is a cryptographic commitment to its definition — two agents using the same handle are provably talking about the same thing.

Before defining a concept from scratch, check if sema already has a word:

  1. sema_search with the idea
  2. sema_resolve to read mechanism and invariants
  3. Use the handle as a load-bearing noun in your text: "This uses StateLock#c9c2 to prevent concurrent mutation"

Not footnotes — actual words you think with.

When the user wants to see patterns visually

If the user asks to "see", "view", "show", or "explore" patterns visually — or asks to see the graph or browse the vocabulary — invoke the sema-ui skill to launch http://localhost:3030. The UI gives them an interactive pattern browser, search, and 3D graph.

Session memory

The server tracks which patterns you've already seen. Subsequent searches return compact results for known patterns (handle + gloss + _seen: true). Just use the handle — the full definition is already in your context. Call sema_resolve only if you need to re-read a pattern's mechanism.

Call sema_reset_session() if your context was compressed or you need full results again.

The workflow

  1. Searchsema_search({ query: "trust model" }) — find existing patterns by meaning
  2. Resolvesema_resolve({ handle: "TrustModel#7859" }) — read full definition, mechanism, invariants
  3. Handshakesema_handshake({ ref: "X#1234" }) — verify exact meaning before relying on a handle
  4. Mintsema_mint({ pattern_json: "..." }) — create a new pattern (rare!)

Switching and managing databases

The CLI and MCP server are separate processes with separate DB state. sema use on the CLI does NOT affect the running MCP server. Always use the MCP tool for switching:

Read the full file on GitHub · 237 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. 6d ago First seen · 237 lines · 39 tokens per session scan A 95975566c5fe

Subscribe to this mod's changes

sema-usage is a skill published in the GitHub repository emergent-wisdom/sema (13 stars, last pushed 5d ago), licensed MIT. It adds 39 tokens to every session and 3,067 once invoked, about $0.0002 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 2026-08-30.