Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/vanterx/mssql-performance-skills/sqlplan-comparenpx skills add vanterx/mssql-performance-skills --skill sqlplan-comparegit clone --depth 1 https://github.com/vanterx/mssql-performance-skillsWrote 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/vanterx/mssql-performance-skills/sqlplan-compare)<a href="https://agentmods.dev/skills/vanterx/mssql-performance-skills/sqlplan-compare"><img src="https://agentmods.dev/badge/skills/vanterx/mssql-performance-skills/sqlplan-compare.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 | $0.00070 | $0.03893 |
| Opus 5 | $0.00035 | $0.01946 |
| Sonnet 5 | $0.00014 | $0.00779 |
| Haiku 4.5 | $0.00007 | $0.00389 |
Grade A, and why
sqlplan-compare 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 3d 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 — 288 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SQL Server Execution Plan Comparison Skill
Purpose
Identify what changed between two execution plans for the same query — one known-good (baseline) and one regressed (new). Produce a side-by-side diff that explains why the query is slower and what to fix. Applies 20 regression checks (C1–C20).
Input
Accept any of:
- Two
.sqlplanfile paths:baseline.sqlplanandnew.sqlplan - Two blocks of raw
.sqlplanXML pasted inline, labeled Baseline and New - A description of both plans if XML is not available
How to Run
- Parse both plans independently
- Extract the comparison metrics listed below for each plan
- Produce a side-by-side diff table, then a findings section for every significant change
- Conclude with a prioritized fix list
Metrics to Compare
Statement-Level
| Metric | Where to Find | Signal |
|---|---|---|
| StatementSubTreeCost | StmtSimple/@StatementSubTreeCost |
> 2× increase = regression |
| DegreeOfParallelism | QueryPlan/@DegreeOfParallelism |
DOP drop = serial plan forced |
| GrantedMemory (KB) | MemoryGrantInfo/@GrantedMemory |
> 2× increase = cardinality inflation |
| MaxUsedMemory (KB) | MemoryGrantInfo/@MaxUsedMemory |
Used > Granted = spill |
| CardinalityEstimationModelVersion | QueryPlan/@CardinalityEstimationModelVersion |
Version drop = compat level change |
| CompileCPU (ms) | StmtSimple/@CompileCPU |
> 2× increase = optimizer struggling |
| MissingIndexGroup count | <MissingIndexes> children |
New suggestions = indexes dropped |
Operator Topology
Compare these for each plan:
- Join count by type — Hash Match, Merge Join, Nested Loops (report count of each)
- Join type changes — Identify any operator that changed type between plans (e.g., Hash → Nested Loops is a regression signal when the table is large)
- New operators — Operators present in the new plan but not the baseline (e.g., Sort, Spool, Key Lookup appearing)
- Removed operators — Operators in baseline but not new (e.g., Seek replaced by Scan)
- Scan vs Seek changes — Any table that changed from Seek to Scan is critical
What ships with it
8 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 3d ago First seen · 288 lines · 70 tokens per session scan A 1ddc8392b441
sqlplan-compare is a skill published in the GitHub repository vanterx/mssql-performance-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 70 tokens to every session and 3,893 once invoked, about $0.0003 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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