Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/metaschema-framework/claude-pluginsnpx agentmods add skills/metaschema-framework/claude-plugins/metapath-expressionsWrote 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.
[](https://agentmods.dev/skills/metaschema-framework/claude-plugins/metapath-expressions)<a href="https://agentmods.dev/skills/metaschema-framework/claude-plugins/metapath-expressions"><img src="https://agentmods.dev/badge/skills/metaschema-framework/claude-plugins/metapath-expressions.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00040 | $0.03014 |
| Opus 5 | $0.00020 | $0.01507 |
| Sonnet 5 | $0.00008 | $0.00603 |
| Haiku 4.5 | $0.00004 | $0.00301 |
Grade A, and why
metapath-expressions 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 8d 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.
How it starts
The opening of the file, as written. The whole thing — 403 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Metapath Expression Language
Metapath is based on XPath 3.1, adapted for Metaschema's data model. This skill covers the expression language used in Metaschema constraints and queries.
Path Expressions
Basic Navigation
| Expression | Description |
|---|---|
. |
Current node (context item) |
.. |
Parent node |
./child |
Child named "child" |
./child/grandchild |
Nested navigation |
.//descendant |
Any descendant named "descendant" |
@flag |
Flag (attribute) named "flag" |
//root |
From document root |
Axis Navigation
| Axis | Description | Example |
|---|---|---|
child:: |
Direct children (default) | child::name = ./name |
parent:: |
Parent node | parent::* |
ancestor:: |
All ancestors | ancestor::catalog |
ancestor-or-self:: |
Ancestors plus current | ancestor-or-self::* |
descendant:: |
All descendants | descendant::item |
descendant-or-self:: |
Descendants plus current | descendant-or-self::* = .// |
self:: |
Current node | self::node() |
preceding-sibling:: |
Preceding siblings | preceding-sibling::item |
following-sibling:: |
Following siblings | following-sibling::item |
Wildcards
| Pattern | Description |
|---|---|
* |
Any element |
@* |
Any flag (attribute) |
node() |
Any node |
Predicates
Filter nodes using conditions in brackets:
./item[@status = 'active']
./user[position() = 1]
./entry[starts-with(@id, 'X-')]
./control[exists(./part)]
./param[@id][not(@class = 'hidden')]
Position Predicates
./item[1] # First item
./item[last()] # Last item
./item[position() > 1] # All but first
./item[position() mod 2 = 0] # Even positions
Operators
Comparison Operators
| Operator | Description | Note |
|---|---|---|
=, != |
General comparison | Compares sequences |
eq, ne |
Value equality | Single values only |
<, >, <=, >= |
General comparison | Compares sequences |
lt, gt, le, ge |
Value comparison | Single values only |
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.
- 8d ago First seen · 403 lines · 40 tokens per session scan A 705c261baf9b
metapath-expressions is a skill published in the GitHub repository metaschema-framework/claude-plugins (10 stars, last pushed 6mo ago), licensed CC0-1.0. It adds 40 tokens to every session and 3,014 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 2026-08-31.
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