OpenRouter Function Calling Agent Skill

Implement function/tool calling with OpenRouter models.

Context cost
7k tokensestimated from the bundle, loaded when it triggers
Bundle
10 files · 28.1 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—v1.20.0
Servers it uses
Noneruns standalone

What it does

Implement function/tool calling with OpenRouter models. Use when building

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md10.6 kB · preview
--- name: openrouter-function-calling allowed-tools: Read, Write, Edit, Grep, Bash(python3:*), Bash(node:*) version: 1.20.0 license: MIT author: Jeremy Longshore <jeremy@intentsolutions.io> tags: - saas - openrouter - function-calling - agents - tools compatibility: Designed for Claude Code ---
21# OpenRouter Function Calling
22
23## Overview
24
25OpenRouter supports OpenAI-compatible tool/function calling across multiple providers. Define tools as JSON Schema, send them with your request, and the model returns structured tool_calls instead of free text. This works with GPT-4o, Claude 3.5, Gemini, and other tool-capable models via the same API. The key difference from direct provider APIs: OpenRouter normalizes the tool calling interface, so the same code works across providers.
26
27## Prerequisites
28
29- An OpenRouter API key (sk-or-v1-...) exported as OPENROUTER_API_KEY — see the openrouter-install-auth skill for setup
30- Python 3.8+ or Node.js 18+ with the OpenAI SDK (pip install openai / npm install openai)
31- A tool-capable model — check the Model Compatibility table below or query /api/v1/models (e.g., openai/gpt-4o, anthropic/claude-3.5-sonnet)
32- Real function implementations to dispatch tool calls to (the execute_tool() dispatcher below stubs get_weather and search_database)
33
34## Instructions
35
361. Pick a model from the Model Compatibility table that supports the features you need (tool calling, JSON mode, parallel tools).
372. Define your tools as JSON Schema per Basic Tool Calling and send them with tool_choice="auto" (or "required" to force a call, or a specific function name).
383. Read response.choices[0].message.tool_calls — each entry carries function.name and JSON-encoded function.arguments to parse with json.loads().
394. For agents, wire the Multi-Turn Tool Loop: append the assistant message, execute each tool via execute_tool(), append role: "tool" results keyed by tool_call_id, and loop until the model returns plain text (bounded by max_rounds).
405. Use the TypeScript Tool Calling section for the identical flow in Node — same schema, same tool_calls shape.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md1,245 words
Files10
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈140
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
6,885
on trigger
The instruction body and 9 supporting files, read only when the skill fires.
3.5%
of a 200k window
Ten skills this size would take about 35% of the window before you open a file.
050k100k150k200k context window

7k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

It asks the agent to write files, using whatever file access your client already has. Whether it reaches the network is not declared.

What it asks for
Writes filesyes
Network accessnot declared

Read from the allowed-tools line of this skill’s own SKILL.md. It also asks for Bash, which could do either, so what is not named there is not ruled out. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

10 files, 28.1 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md10.6 kB
  • references/advanced-tool-definitions.md3.0 kB
  • references/basic-function-calling.md3.1 kB
  • references/errors.md0.5 kB
  • references/examples.md4.5 kB
  • references/forced-tool-use.md0.8 kB
  • references/model-compatibility.md1.0 kB
  • references/parallel-tool-calls.md1.1 kB
  • references/streaming-with-tools.md2.0 kB
  • references/tool-router.md1.5 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 10 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# OpenRouter Function Calling · 7k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/openrouter-function-calling/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/openrouter-function-calling" ] && { [ ! -e .claude/skills/openrouter-function-calling ] || { mv .claude/skills/openrouter-function-calling "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/openrouter-function-calling" .claude/skills/ && echo "Installed .claude/skills/openrouter-function-calling"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add jeremylongshore/openrouter-function-calling

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/openrouter-function-calling/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/openrouter-function-calling/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/openrouter-function-calling" ] && { [ ! -e ~/.claude/skills/openrouter-function-calling ] || { mv ~/.claude/skills/openrouter-function-calling "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/openrouter-function-calling" ~/.claude/skills/ && echo "Installed ~/.claude/skills/openrouter-function-calling" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/openrouter-function-calling/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Version1.20.0
Publishedno release date on file
PriceFree
Referencejeremylongshore/openrouter-function-calling

Versions

v1.20.0 is what is on the shelf; no release here carries a date. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v1.20.0
  • No earlier releases have been published to the marketplace.
Pinning

The install command always fetches the release that is current the day you run it — v1.20.0 today — and cannot ask for an earlier one. The copy on your disk does not change until you run it again.

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