Evidence Grounding
How MARCUS handles uncertainty, authority, and the boundary between supported and unsupported answers.
Evidence grounding is the core safety property of MARCUS. The system is designed to answer from retrieved source material and to show that source material back to the user.
Grounding is what turns MARCUS from a general-purpose text generator into a corpus-based evidence assistant.
What Grounded Means In MARCUS
A grounded answer is an answer assembled from retrieved passages in the current project, with citations that point back to those passages or their parent sources.
In practical terms, that means:
- the answer should be tied to your uploaded evidence
- the user should be able to inspect that evidence
- the answer should reflect the limits of the available corpus
Grounding is not the same thing as certainty. It is the discipline of tying claims back to visible support.
What Grounding Protects Against
Grounding reduces the risk of:
- unsupported claims presented as if they came from your documents
- drift into general background knowledge when the task is supposed to be project-specific
- answers that sound polished but cannot be audited
It does not eliminate all failure modes, but it makes them more visible and more manageable.
What Grounding Does Not Guarantee
Grounding does not guarantee:
- that the project contains the complete evidence base
- that the highest-authority source was uploaded
- that conflicting sources have been resolved automatically
- that the cited source is the right fit for a specific patient or operational exception
- that the answer is complete just because it is cited
This is why MARCUS still expects user judgment.
The Boundary Between Supported And Unsupported
A useful way to think about grounded output is as a spectrum:
- well supported: the answer is clearly backed by relevant, authoritative citations
- partially supported: the answer has some evidence, but the corpus is thin or the citations are narrow
- weakly supported: the evidence exists but is limited, low-authority, or only loosely connected
- unsupported for this corpus: the project does not really contain what is needed to answer confidently
MARCUS is safest when the user can recognize which part of that spectrum an answer belongs to.
How MARCUS Handles Uncertainty
When evidence is sparse or weak, MARCUS should trend toward:
- lower apparent coverage or confidence
- narrower, more qualified answers
- clearer citation dependency
If the corpus does not support the question well, the safest response is usually to refine the scope or add better sources rather than force a highly confident synthesis.
Why Coverage Matters
Coverage is not exactly the same as correctness. Coverage is about whether the corpus seems to contain enough relevant evidence for the question asked.
That means:
- a correct-looking answer with low coverage still deserves caution
- a high-authority source with low coverage may still leave important gaps
- a multi-source answer with strong coverage is usually easier to trust, though still not beyond review
Coverage is one of the product's most important honesty signals.
Why Authority Matters
Authority helps decide how much weight a source should carry relative to others. A level 5 guideline and a level 1 note should not be treated as interchangeable even if both mention the same topic.
Authority is part of grounding because support is not just about whether a source exists. It is also about whether that source is the kind of evidence you would want supporting the answer.
Local Applicability Matters Too
An answer can be well grounded in the wrong kind of source for your use case.
Examples:
- a general guideline may be authoritative but not the controlling local workflow
- a local policy may be operationally controlling even if it is not the strongest general evidence source
- an educational note may describe the topic well but still be the wrong basis for a live decision
This is why grounding should always be interpreted with context, not treated as a magic stamp of correctness.
How Users Should Read A Grounded Answer
When an answer matters, ask:
- Do the citations actually support the main claim?
- Are the sources strong enough for this decision?
- Is the answer drawing from the right kind of source, not just any source?
- Does the corpus appear complete enough for the question?
- If sources disagree, is that conflict visible or hidden?
This is the practical discipline of evidence-grounded use.
When To Open The Citations Immediately
Open the citations when:
- the answer turns on a threshold
- two sources might conflict
- the question affects escalation, discharge, medication, or another high-stakes decision
- the answer sounds stronger than you expected
- coverage is low or the source quality is unclear
In MARCUS, opening citations is not a sign of distrust. It is the normal completion of the workflow.
Common Misunderstandings About Grounding
| Misunderstanding | Better interpretation |
|---|---|
| "It has citations, so it must be complete." | Citations show support, not completeness. |
| "Low coverage means the answer is definitely wrong." | Low coverage means the corpus support is thin; the answer may still contain useful partial support. |
| "High authority means I do not need to verify the answer." | Authority helps, but verification still matters. |
| "If the answer sounds good, the grounding is probably good too." | Fluency and grounding are different things. |
The Core User Responsibility
MARCUS is built to make source review faster, not optional. The user's job is not to distrust every answer reflexively. The user's job is to use citations, authority, and coverage cues to judge how strongly the corpus really supports the conclusion.
One Practical Summary
Grounding means MARCUS should show its work. Safe use means you still read that work when the decision matters.