Agent skill

Structured Tool Reasoning

by VectorSpaceLab in VectorSpaceLab/AREX-Skill

Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend…

Apache-2.0Auto-check passedAI & LLM Engineering

Install Structured Tool Reasoning

skills CLI
$ npx skills add VectorSpaceLab/AREX-Skill --skill structured-tool-reasoning -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install VectorSpaceLab/AREX-Skill structured-tool-reasoning --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/VectorSpaceLab/AREX-Skill.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/repositories/repo-skills/vllm/sub-skills/structured-tool-reasoning .claude/skills/structured-tool-reasoning && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
structured-tool-reasoning
GitHub stars
328
Token cost
~823 tokens
SKILL.md length
282 words
Files
6 (incl. scripts, references)
Skills in repo
157
Repo updated
First seen
Licence
Apache-2.0

At a glance

Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend…

  • Tasks that involve Structured output and tool calling
  • SKILL.md covers Route by Task, Safe Local Helper, Boundaries and Hardware and Runtime Notes
  • Runs Python scripts from its folder; calls python
  • Tasks that involve LLM inference and serving

What it does

Structured Tool Reasoning is an agent skill from VectorSpaceLab/AREX-Skill. Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend troubleshooting.

Its SKILL.md is about 820 tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including scripts and reference files (for example `references/reasoning-parsers.md`, `references/structured-outputs.md` and `references/tool-calling.md`).

It sits in AI & LLM Engineering, covering Structured output and tool calling and LLM inference and serving. It works with vLLM and OpenAI. The repository describes itself as: A Skill Library for Automated Machine Learning. The licence is Apache-2.0.

When your agent uses it

  • Tasks that involve Structured output and tool calling
  • Tasks that involve LLM inference and serving

Example prompts

  • “/structured-tool-reasoning”

Requirements

  • Python 3

What it can do on your machine

Read from SKILL.md and the folder at commit ac3fe1a. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • python

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Structured Tool Reasoning loads about 823 tokens when it runs, and up to ~9.7k if it reads all its reference files. Until then it costs about 59 tokens; SKILL.md has 282 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~59
When it runs · the whole SKILL.md, loaded when a task matches
~823
With references · SKILL.md plus every file in references/, read only if the agent opens them
~9.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from VectorSpaceLab/AREX-Skill at commit ac3fe1a, republished under its Apache-2.0 licence (© VectorSpaceLab). 282 words, ~823 tokens.

Download SKILL.mdSave it as .claude/skills/structured-tool-reasoning/SKILL.md (or your agent's skills folder). This skill also uses 5 other files; get the full folder from GitHub.
name
structured-tool-reasoning
description
Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend troubleshooting.
disable-model-invocation
true
metadata.disco-role
operating
license
Apache 2.0

Structured Tool Reasoning

Use this sub-skill when the task involves constrained generation, OpenAI-compatible response_format or structured_outputs, tool/function calling, reasoning parser output, or debugging parser/template/backend behavior in vLLM.

Route by Task

  • For JSON schema, JSON object, choice, regex, grammar, or structural-tag constraints, read references/structured-outputs.md.
  • For OpenAI-compatible tools, tool_choice, auto tool choice, strict tool schemas, parser names, chat templates, and streaming tool-call assembly, read references/tool-calling.md.
  • For --reasoning-parser, reasoning fields, reasoning streaming deltas, thinking controls, and combining reasoning with tools or structured outputs, read references/reasoning-parsers.md.
  • For unsupported schema keywords, invalid grammars, backend dependency issues, parser name mismatches, incompatible chat templates, missing streamed tool calls, or absent reasoning content, read references/troubleshooting.md.

Safe Local Helper

Use the bundled validator before contacting a server when a user provides a request fragment:

bash
# From this sub-skill directory:
python scripts/validate_structured_request.py --input request.json
python scripts/validate_structured_request.py --example tool-streaming

# From the root vLLM skill directory:
python sub-skills/structured-tool-reasoning/scripts/validate_structured_request.py --input request.json

The helper checks request-shape consistency for response_format, structured_outputs, tools, tool_choice, reasoning flags, common backend compatibility risks, and streaming tool-call handling. It does not import vLLM, download models, start a server, execute tools, or call external APIs.

Boundaries

  • Route general server startup, authentication, host/port, OpenAI endpoint coverage, and deployment layout to ../openai-serving/ when present.
  • Route basic LLM.generate or LLM.chat setup without structured constraints to ../offline-inference/ when present.
  • Route multimodal, pooling, embeddings, adapters, and LoRA-specific requests to ../modalities-adapters-pooling/ when present.
  • Route performance tuning of structured decoding backends, throughput, batching, and benchmark questions to ../deployment-performance/ when present.

Hardware and Runtime Notes

  • Offline and serving examples require user-provided models and hardware appropriate for the selected model; CPU-only or precompiled inspection environments prove imports and signatures, not GPU throughput.
  • OpenAI-compatible examples assume the user already has a running vLLM server exposing /v1.
  • Tool execution is always application-owned: vLLM returns tool-call names and argument strings; caller code validates and executes the actual functions.

© VectorSpaceLab, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (scripts, references) in skills/repositories/repo-skills/vllm/sub-skills/structured-tool-reasoning of VectorSpaceLab/AREX-Skill.

  • SKILL.md
  • references/reasoning-parsers.md
  • references/structured-outputs.md
  • references/tool-calling.md
  • references/troubleshooting.md
  • scripts/validate_structured_request.py

Open the folder on GitHubat commit ac3fe1a

Compare with similar skills

Structured Tool Reasoning next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Structured Tool Reasoning compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Structured Tool Reasoning this skillVectorSpaceLab/AREX-Skill328—~823Automated safety check: PassApache-2.0
VllmPrism-Shadow/penguin-harness2.5k—~1kAutomated safety check: PassApache-2.0
Aider DelegateamElnagdy/delegate-skills2.3k3 repos~3kAutomated safety check: PassMIT
Perfupraullenchai/Rapid-MLX3.9k—~1.6kAutomated safety check: NotesCustom licence
Model Serving MinefieldBlackwellboy/model-serving-minefield135—~2.1kAutomated safety check: PassMIT
Outlines Structured GenerationOrchestra-Research/AI-Research-SKILLs13k10 repos~4kAutomated safety check: PassMIT

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Works with

Questions about Structured Tool Reasoning

What does Structured Tool Reasoning do?

Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend…. Structured Tool Reasoning is an agent skill from VectorSpaceLab/AREX-Skill. Use this vLLM sub-skill for structured outputs, JSON/regex/grammar constraints, tool calling, reasoning parsers, chat-template/tool-parser routing, streaming tool-call deltas, and parser/backend troubleshooting.

When should I use Structured Tool Reasoning?

Structured Tool Reasoning fits situations like: tasks that involve Structured output and tool calling; tasks that involve LLM inference and serving.

How do I install Structured Tool Reasoning in Claude Code?

Run `npx skills add VectorSpaceLab/AREX-Skill --skill structured-tool-reasoning -a claude-code`. Or copy the skill folder (skills/repositories/repo-skills/vllm/sub-skills/structured-tool-reasoning in VectorSpaceLab/AREX-Skill) into .claude/skills/structured-tool-reasoning in your project. Claude Code loads it when a task matches its description.

How do I install Structured Tool Reasoning in Codex?

Run `npx skills add VectorSpaceLab/AREX-Skill --skill structured-tool-reasoning -a codex`. Or copy the skill folder (skills/repositories/repo-skills/vllm/sub-skills/structured-tool-reasoning in VectorSpaceLab/AREX-Skill) into .agents/skills/structured-tool-reasoning in your project. Codex loads it when a task matches its description.

Can I use Structured Tool Reasoning in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add VectorSpaceLab/AREX-Skill --skill structured-tool-reasoning -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/structured-tool-reasoning, .gemini/skills/structured-tool-reasoning, .github/skills/structured-tool-reasoning and .opencode/skills/structured-tool-reasoning in your project.

What does Structured Tool Reasoning need to run?

Going by SKILL.md and its folder, Structured Tool Reasoning needs Python for the scripts in its folder and the command-line tools its instructions call (python). Our summary lists: Python 3.

Does Structured Tool Reasoning access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Structured Tool Reasoning safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Structured Tool Reasoning use?

Structured Tool Reasoning is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Structured Tool Reasoning use?

About 823 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 8.8k tokens, read only when the agent opens those files.

What are the alternatives to Structured Tool Reasoning?

Skills that share tags, products or a category with Structured Tool Reasoning: Vllm (Prism-Shadow/penguin-harness, 2.5k stars), Aider Delegate (amElnagdy/delegate-skills, 2.3k stars), Perfup (raullenchai/Rapid-MLX, 3.9k stars) and Model Serving Minefield (Blackwellboy/model-serving-minefield, 135 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Structured Tool Reasoning?

VectorSpaceLab (a GitHub organization) maintains it in VectorSpaceLab/AREX-Skill, which has 328 GitHub stars. The repository holds 157 skills in this directory. The repository was last updated on September 3, 2026.

Source: VectorSpaceLab/AREX-Skill on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.