skill-authoring

> Host: Codex CLI — This skill was designed for Claude Code and adapted for Codex.

> Cross-reference commands use installed skill names in Codex rather than /octo:* slash commands.

> Use the active Codex shell and subagent tools. Do not claim a provider, model, or host subagent is available until the current session exposes it.

> For host tool equivalents, see skills/blocks/codex-host-adapter.md.

Skill Authoring

Load skills/blocks/engineering-method-selection.md from the installed plugin

and apply only the methods relevant to this task. Preserve this entry point's

execution contract and output format. Read referenced skills as instructions;

do not invoke the current command recursively or add provider calls from a seat.

Domain language

Load skills/blocks/domain-modeling.md when a skill discusses providers, models,

access, billing, reviewers, or votes. Reuse the shared definitions instead of

inventing local synonyms. State the source and time of observations. Never infer

authentication, entitlement, billing mode, quota, or model-family independence

from a binary or transport name alone.

A skill exists to get determinism out of a stochastic system. Predictability

is the goal, and it means the agent takes the same process every run — not that

it produces the same output. Every rule below serves that.

docs/PLUGIN-ASSEMBLY-STANDARD.md already fixes the structure a skill body

should take. This is about what makes the content inside that structure work.

Adapted from writing-great-skills in

mattpocock/skills (MIT), with the

invocation section rewritten for how this plugin actually loads skills.

When To Use

• Writing a new skill, or reviewing one in a PR.
• A skill fires when it should not, or fails to fire when it should.
• A skill behaves differently run to run on the same input.
• Deciding whether something should be a skill at all, or a command, or prose in

CLAUDE.md.

When Not To Use

• For the mechanical checklist — file layout, registration, required sections.

That is docs/PLUGIN-ASSEMBLY-STANDARD.md and the CI suites.

• For writing prompts that are not skills. That is skill-meta-prompt.

Inputs

The skill under construction or review, and an honest answer to: what should the

agent do differently because this exists?

Workflow

Invocation: explicit by default

Every shipped command and skill carries disable-model-invocation: true.

Claude Code therefore keeps Octopus out of model context until the user chooses

an /octo:* command. This is a hard platform gate, not a prose reminder.

Command bodies that need reusable instructions load the entire source file

directly from

${HOME}/.claude-octopus/plugin/.claude/skills/<name>/SKILL.md; they do not call

the Skill tool. ${HOME}/.claude-octopus/plugin is the stable, self-healed path

available to model tool calls; CLAUDE_PLUGIN_ROOT is a hook/runtime variable

and may be absent from that context. The command must treat the loaded body as

the active instructions in the current conversation, follow its steps in order,

and pass the user's text as workflow arguments rather than executable path

content. This keeps explicit commands composable without reopening automatic

model invocation.

Plain-language routing is a separate, legacy-compatible opt-in controlled by

OCTOPUS_AUTO_ROUTER_MODE=suggest|invoke. Its default is off. New skills must

never depend on prompt-keyword auto-routing for reachability.

Writing the description

The description does two jobs: say what the skill is, and list the branches that

should trigger it. It sits in the context window every turn, so it earns harder

pruning than the body.

• Lead with the word that does the invoking.
• One trigger per branch. Synonyms that rename the same branch are

duplication: "use for test-first development … when the user wants TDD" is one

branch written twice.

• Cut identity that the body already carries. Triggers, plus any "when another

skill needs this" clause, and nothing else.

• Beware collision. With this many skills the scarce resource is trigger space,

not skill count. Before adding a trigger phrase, check whether an existing

skill or hooks/user-prompt-submit.sh already claims it. The hook is opt-in,

but overlapping phrases still degrade routing for users who enable it.

Information hierarchy

Content is either a step (an ordered action) or reference (a rule or fact

consulted on demand). A skill can be all of one, or both. Place each piece on the

rung it belongs:

1. In-skill step — what the agent does, in order.
2. In-skill reference — consulted while working. A flat set of peer rules is

a legitimate shape, not a smell.

1. External reference — pushed into a sibling file and reached by a pointer,

loaded only when the pointer fires. skills/blocks/ is where shared ones live.

Push too little down and the top bloats; push too much and the agent never finds

what it needs. Branching is the cleanest test: inline what every run needs, push

behind a pointer what only some runs reach.

Completion criteria

Every step ends on a condition that says the work is done. Make it:

• Checkable — can the agent tell done from not-done without guessing?
• Exhaustive where it matters — "every changed file accounted for" rather

than "review the changes". A vague criterion invites stopping early on

something that looks finished.

"Produce a summary" is not a completion criterion. "Every boundary in the table

maps to a real handoff in the setup" is.

Enforcement, and its cost

A body that names the orchestrator script directly is required by

tests/unit/test-mandatory-compliance.sh to carry a MANDATORY COMPLIANCE block

and a PROHIBITED list. That is deliberate for skills that dispatch providers

and spend money. It is dead weight on an advisory skill — so if a skill only

advises, refer to workflows by their /octo: command names and skip the

ceremony rather than adding a compliance block nobody needs.

Provider Or Data Priority

1. The existing skills, as worked examples of the conventions.
2. docs/PLUGIN-ASSEMBLY-STANDARD.md for required structure.
3. The CI suites, which encode constraints prose does not mention.

Stop Or Checkpoint Rules

• Stop before adding a skill whose triggers overlap an existing one. Extend the

existing skill instead; a near-duplicate makes both harder to reach.

• Stop if the answer to "what does the agent do differently" is "nothing it

would not have done anyway".

• If the content is one paragraph of advice with no process, it belongs in the

skill that already covers the area, not in a new file.

Output Contract

When reviewing, report:

1. Verdict — ship, revise, or fold into an existing skill.
2. Predictability risks — where two runs would diverge.
3. Trigger collisions — which existing skill or hook arm competes.
4. Criteria that are not checkable — quoted, with a replacement.
5. Misplaced content — what should move up or down the hierarchy.

Verification

• The description names distinct branches, with no synonym pairs.
• Every step has a criterion the agent can evaluate.
• No trigger phrase collides with hooks/user-prompt-submit.sh or an existing

skill's description.

• The skill is registered in .claude-plugin/plugin.json and make sync is

clean.

• It declares disable-model-invocation: true, and any command that composes it

loads its source file directly.

• tests/unit/test-explicit-activation.sh passes.