Whatwg URL Specs

What it does

When your agent uses it

• A URL test fails
• Parser/serializer/host/IDNA behavior looks wrong
• You need the exact spec section
• Algorithm steps

Example prompts

• “/whatwg-url-specs”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Reproduce: run the failing focused test (see the webpp-build-test skill), note the exact input/output mismatch.
2. 2Locate the spec part: find the section/algorithm/state in the map below, or run
3. 3Read the normative text: query the id of that section/algorithm/state (e.g. tools/whatwg-url-specs host-state),
4. 4Compare step-by-step with the implementation (webpp/uri/parser/*.hpp) and the tests
5. 5Treat discrepancies per the pinned-standard rule below: tests + implementation win unless the task is to update

What it can do on your machine

Read from SKILL.md and the folder at commit 66a52aa. 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

  No scripts in the folder and no shell commands in SKILL.md (its code samples are bash).

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

• Network

  Hosts in commands or code, which the agent is likely to contact:

  • url.spec.whatwg.org

  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

Whatwg URL Specs loads about 1.9k tokens when it runs. Until then it costs about 82 tokens; SKILL.md has 597 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~82

When it runs · the whole SKILL.md, loaded when a task matches

~1.9k

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

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); files beside SKILL.md are not scanned.

SKILL.md

The full file from the-moisrex/webpp at commit 66a52aa, republished under its MIT licence (© the-moisrex). 597 words, ~1,865 tokens.

name

whatwg-url-specs

description

Debug Web++ URL/URI behavior against the authoritative WHATWG URL Standard using the repo-local tools/whatwg-url-specs command. Use when a URL test fails, parser/serializer/host/IDNA behavior looks wrong, or you need the exact spec section, algorithm steps, parser state, or definition behind a URI requirement.

▪ Abstract
▪ Table of Contents
▪ Goals
▪ 1.Infrastructure
  ▪ 1.1.Writing
  ▪ 1.2.Parsers
  ▪ 1.3.Percent-encoded bytes
▪ 2.Security considerations
▪ 3.Hosts (domains and IP addresses)
  ▪ 3.1.Host representation
  ▪ 3.2.Host miscellaneous
  ▪ 3.3.IDNA
  ▪ 3.4.Host writing
  ▪ 3.5.Host parsing
  ▪ 3.6.Host serializing
  ▪ 3.7.Host equivalence
▪ 4.URLs
  ▪ 4.1.URL representation
  ▪ 4.2.URL miscellaneous
  ▪ 4.3.URL writing
  ▪ 4.4.URL parsing
  ▪ 4.5.URL serializing
  ▪ 4.6.URL equivalence
  ▪ 4.7.Origin
  ▪ 4.8.URL rendering
    ▪ 4.8.1.Simplify non-human-readable or irrelevant components
    ▪ 4.8.2.Elision
    ▪ 4.8.3.Internationalization and special characters
▪ 5.application/x-www-form-urlencoded
  ▪ 5.1.application/x-www-form-urlencodedparsing
  ▪ 5.2.application/x-www-form-urlencodedserializing
  ▪ 5.3.Hooks
▪ 6.API
  ▪ 6.1.URL class
  ▪ 6.2.URLSearchParams class
  ▪ 6.3.URL APIs elsewhere
▪ Acknowledgments
▪ Intellectual property rights
▪ Index
  ▪ Terms defined by this specification
  ▪ Terms defined by reference
▪ References
  ▪ Normative References
  ▪ Non-Normative References
▪ IDL Index

tools/whatwg-url-specs list                # full section/definition/algorithm tree
tools/whatwg-url-specs --algorithm list    # algorithms only
tools/whatwg-url-specs --algorithm host parser   # restrict a query to algorithms
tools/whatwg-url-specs --html url-parsing # raw HTML instead of Markdown
tools/whatwg-url-specs --verbose ...       # cache/parse progress on stderr
tools/whatwg-url-specs --clean-cache       # drop cached spec (fresh download next run)

# 1. phrase -> containing id (hyphenate/lowercase first; grep `list` when unsure)
tools/whatwg-url-specs list | grep -i "host-state"
tools/whatwg-url-specs host-state                 # dumps that state's steps

# 2. or grep a section dump (`url-parsing` contains nested state steps too);
#    strip backticks so a verbatim sentence matches the Markdown output
tools/whatwg-url-specs url-parsing | tr -d '\`' | grep -n "If url is special and buffer is the empty string"

# 3. if the sentence is not in the dumped section, grep the likely one instead
#    (here: the step lives in the serializer, not in `url-parsing`)
tools/whatwg-url-specs url-serializer | grep -n "fragment is non-null"

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

Files

Just SKILL.md in .agents/skills/whatwg-url-specs of the-moisrex/webpp.

Open the folder on GitHubat commit 66a52aa