---
name: cross-source-synthesis
description: "Merge several sources into one theme-organized narrative where every claim is traced to a source and points of agreement and disagreement across sources are named explicitly — instead of summarizing each source in turn. Use when someone hands you multiple documents, notes, or search results and asks what they collectively say about a topic. Do NOT use for summarizing a single source, or for answering one factual question from a knowledge base."
metadata:
  decimalai-skill-id: "72160dd1-b9ec-4dcd-be63-30aa92553234"
  decimalai-version-id: "2f420dce-b00c-4aae-8e58-af4d5beccbe4"
  decimalai-version: "1"
  decimalai-body-sha256: "b630d6fdd496f7bb7d8379db095eb04fedce9faba1f86a3b63ae2817d84fe47c"
  decimalai-name: "cross-source-synthesis"
  decimalai-format: "1"
  decimalai-invocation: "model"
  decimalai-category: "research"
  decimalai-source: "https://app.decimal.ai/s/cross-source-synthesis@1/SKILL.md"
---
# Cross-Source Synthesis

## What this does

Takes several sources on one topic — research summaries, analyst notes, retrieved
passages, meeting recaps — and merges them into **one narrative organized by theme**, in
which every claim is **traceable to the source it came from** and the places where sources
**agree** or **disagree** are called out by name.

The base model, handed a stack of sources and asked "what do these say about X?", walks the
sources one at a time and emits a summary per source. The reader is left to notice that two
sources corroborate each other, or that a third flatly contradicts them. This skill converts
that per-source rundown into a synthesis: the structure follows the topic, not the source
list, and the tensions between sources become the point rather than an accident the reader
has to reconstruct.

## When to use / when NOT to

**Use when:** the input is two or more sources on a shared topic and the ask is what they
collectively say — "pull these together", "what's the overall picture across these notes",
"weave these reports into one account".

**Do NOT use when:** there is a single source to condense (that is summarization); the ask is
one factual lookup answered from a knowledge base; or the task is generation with no sources
to merge.

## Rules

Follow all six, every time.

1. **Organize by theme, not by source.** Build the output around the topics and findings that
   recur across the sources. Give each theme its own section or paragraph. Never produce a
   "Source 1 says… Source 2 says…" walk through the sources in order — that is the default
   this skill exists to replace.

2. **Trace every claim.** Every factual statement carries a marker for the source(s) it rests
   on (e.g. a trailing `[1]`, or "per the survey"), so a reader can check it. A synthesized
   sentence backed by three sources names all three.

3. **Name agreement.** Where two or more sources report the same finding, say so in words
   ("both the trial and the field study find…"). Corroboration across independent sources is
   a confidence signal — surface it, don't let it read as one uncited fact.

4. **Name conflict.** Where sources disagree, state the disagreement plainly, give both sides,
   and attribute each side to its source. Never silently pick the one you like, never average
   two conflicting numbers into one figure, and never phrase incompatible claims so they sound
   compatible.

5. **Stay inside the sources.** Do not add facts from your own training as if they came from
   the sources. Where the sources are silent or thin on a point, say the sources don't cover
   it rather than filling the gap from memory.

6. **Cover every source.** A source that contributes a distinct claim must appear somewhere in
   the synthesis — including the outlier. Do not drop an inconvenient source to make the story
   tidier; an outlier that disagrees is exactly what Rule 4 exists to surface.

## Worked example

**Sources given** (topic: the four-day work week):
- [1] A UK trial reported no drop in output after hours were cut to four days.
- [2] An Icelandic programme found output held steady or rose across most workplaces.
- [3] A manufacturing survey found output fell about 8% on the compressed schedule.

**BEFORE (base default — per-source rundown, tension buried):**
> Source [1] describes a UK trial where output did not drop. Source [2] describes an
> Icelandic programme where output stayed the same or increased. Source [3] describes a
> manufacturing survey where output dropped by roughly 8%.

The reader has to notice for themselves that [1] and [2] line up and [3] breaks from them.

**AFTER (synthesis — themed, traced, tensions named):**
> **Overall effect on output.** In office and public-sector settings the sources agree the
> four-day week did not cost output: the UK trial saw no drop [1] and the Icelandic programme
> saw output hold steady or rise [2]. **The manufacturing evidence conflicts with this:** a
> survey of compressed-schedule manufacturers found output fell about 8% [3] — the one source
> pointing the other way, and it covers a different sector than [1] and [2], which may explain
> the split.

## Edge cases

- **Sources agree completely.** Still name the corroboration (Rule 3); do not manufacture a
  conflict that isn't there.
- **Sources cover different sub-topics rather than clashing.** They are complementary, not
  conflicting — organize by sub-topic and note that each source covers a different facet.
- **A source is silent on the question.** Say so; silence is not agreement.
- **Only a partial conflict** (agree on direction, differ on magnitude). Name it as a
  disagreement about size, with both figures and their sources — do not round it away.

## Do / Don't

- **Do** lead each section with the finding; append the source markers.
- **Don't** structure the answer as one block per source.
- **Do** write "these disagree" out loud when they do.
- **Don't** average or split-the-difference two conflicting numbers into one.
- **Do** keep the outlier in.
- **Don't** import outside facts to smooth over a gap between sources.

## Common mistakes (the base's defaults)

- Walking the sources in order instead of organizing by theme.
- Presenting two contradictory claims back to back without saying they contradict.
- Silently averaging conflicting figures, or quoting only one of them.
- Dropping the lone dissenting source so the narrative is cleaner.
- Adding a "well-known" fact from training and leaving it uncited among the sourced claims.

## Quick checklist

- [ ] Structure follows themes, not the source list.
- [ ] Every claim has a source marker.
- [ ] Agreements between sources stated in words.
- [ ] Conflicts stated in words, both sides attributed, nothing averaged.
- [ ] Every source that adds a distinct claim appears, outliers included.
- [ ] No un-sourced outside facts.