Grip strength, pain (0–10 NRS), waist circumference, and waist-to-height
existed in the measurement enum, signal registry, and FHIR export but had
no web entry, no detail page, single non-sex-aware bands, and a split-brain
MCP exposure. This closes those gaps.
Web capture: the four signals join the manual measurement form, so a
web-only self-hoster can log them (the iOS client and the measurements API
already could).
Detail pages: flip detailPage on for the four signals and mount each on the
shared HealthKit metric template (chart, stat strip, Coach-read strip,
assessment card) via routed sub-pages and tab-strip pills, the same detail
spine every other metric carries.
Sex-aware bands: grip strength (EWGSOP2 men 27 / women 16 kg) and waist
(WHO men 94 / women 80 cm) now classify by the profile sex through the
age/sex norm resolver the assessment already threads; the resolver also
returns a sex-specific, age-independent band when no date of birth is set.
Fix the waist-to-height boundary so the NICE >= 0.5 rule is correct (the
last in-range value is 0.49).
MCP single source of truth: decouple the registry mcp facet from the Coach
snapshot — a signal can be MCP-readable without being on the Coach surface.
Mark the four physical signals mcp:true, derive the MCP rich-reads clinical
set from the registry flag instead of a duplicate allowlist, and relax the
invariant to coachSnapshot implies mcp (not the reverse). PHQ-9 / GAD-7 and
the environmental signals stay mcp:false and unreachable. compare_metric and
detect_changepoints now advertise clinical-signal support to match
get_metric_baseline.
Bring the new physical clinical signals onto the MCP read surface through
the existing rollup-backed reads. Grip strength, pain (0-10 NRS), waist
circumference, and waist-to-height ratio now resolve in get_metric_baseline,
compare_metric, and detect_changepoints, are discoverable through search
(present-only), and hydrate through fetch (metric:<KEY>).
These signals sit off the Coach snapshot by design, so the MCP layer owns
an explicit exposure allowlist and consumes the signal registry only for
grounding (backing measurement type, unit, population band). The PHQ-9 /
GAD-7 mental-health screeners and the environmental signals are absent from
the allowlist, so they never resolve through any read tool. The longevity
lab panel is already reachable through get_labs and the lab resource
template; no change needed there.
The confirm:false preview echoed the would-be record without running the
type / range / instant validation, so a preview could show a value the
commit then refused. Run the same shared validation in the preview and
surface wouldFail with the error + reason the commit would return, so a
preview and its commit never disagree.
Also note at the REST read-method allowlist that the MCP-audience guard
assumes GET/HEAD/OPTIONS are side-effect-free — a future side-effecting
GET must revisit that audience binding.
Add three grounded read tools, each a thin façade over an existing
server-authoritative engine (no new analytics, userId from the session):
- get_medication_schedule: next-due / overdue per active medication via
the canonical recurrence engine (computeDisplayDue), with as-needed
flagged and no scheduled due time.
- get_integration_status: per-provider sync health (connected, last sync,
reauth-required/failing) from the integration-status ledger, so a user
can see why their data is stale. No secrets or tokens.
- get_preventive_care: the user's already-configured Vorsorge reminders
with their persisted next-due dates and an overdue flag; it surfaces
configured reminders only and invents no screening logic.
Each declares an output schema, read-only annotations, and {present:false}
on absence. Page the search tool across the full assembled result set
(the prior 200-row scan made later items unreachable even through the
cursor) and give each result a per-item deep link where an id exists.
The doctor-visit summariser was duplicated and had drifted: the
healthlog://report/doctor-visit resource omitted mood, the glucose
panel, the wellness composites, and illness episodes that the
doctor_visit_summary prompt already carried. Extract one shared reducer
(doctor-visit-summary.ts) using the richer superset and have both
surfaces call it, so they ground identically and a future change reaches
both wires at once. Both keep the grounded latest+aggregate shape and
omit absent sections honestly.
The MCP measurement and blood-pressure write tools accepted a
client-supplied measuredAt with no temporal bound and persisted it
verbatim, so a far-future or ancient instant could poison "latest"
reads and rollup buckets. Bound it through the shared entry-instant
validator both manual capture paths use — no future beyond a 5-minute
clock-skew tolerance, nothing before 1900 — inside the write cores, and
return the structured out_of_range refusal rather than throwing.
Extract the type/range/instant checks into shared pre-write validators so
the same verdict can be reused by the confirm-gate preview.
Bridge the five already-built, grounded Coach retrieval tools the
inventory already advertised but the wire was missing — closing the
advertise-but-missing self-inconsistency — each a thin wrapper over the
existing read with the same gates and present:false contract. Add a
multi-metric fan-out that loops the single-metric read, and a per-analyte
lab-history mode on the labs read. Declare a structured output schema on
every remaining tool so structured content validates for both a miss and
a hit. Page the large reads (search, lab history, multi-metric) behind an
opaque cursor. Return plain-text, citation-ready summaries from fetch
with per-item deep links instead of a JSON dump.
Add an optional explicit {from,to} range to the comparison and
changepoint reads, served over the same rollup tier the five fixed
trailing windows use (reach back to the lower bound, filter to the
span) — so a before-vs-after-a-date question is answerable without
recomputing analytics. Add a per-analyte lab trajectory read (latest to
recent history) over the existing lab resolver, page-bounded so a heavy
panel cannot balloon the response. Introduce an opaque, stable base64url
cursor helper that decodes any malformed or foreign token to the first
page rather than throwing.
Blood pressure is two values, so it cannot ride the single-value
log_measurement tool. Add log_blood_pressure: it writes the systolic and
diastolic rows atomically under one shared idempotency namespace and one
measured-at instant, range-validates each value, rejects an implausible
pair (systolic at or below diastolic), and keeps the same confirm-flag
preview gate, per-credential write budget, MCP provenance, and audit
trail the existing writes use. Declare a structured output schema on
every write tool so a preview, a commit, an already-logged no-op, and a
refusal all validate as structured content.
Fill the discoverable half of the MCP server. Add RFC 6570 resource
templates for per-item reads — healthlog://metric/{type},
healthlog://metric/{type}/{window}, healthlog://lab/{analyte},
healthlog://medication/{id}, healthlog://report/doctor-visit/{window} —
plus fixed resources for the biomarker catalogue, the data inventory, and
the default doctor-visit summary. Each template is a thin facade over the
same server-authoritative read its matching tool already uses, scoped to
the session user; a foreign id resolves to { present: false }, never
another tenant's row.
Wire user-scoped argument completion and listing on the templates: window
completes the fixed enum, metric and analyte complete only from the user's
own inventory and lab set, so autocomplete doubles as honest discovery.
State the data-grounding contract once in the server instructions —
server-authoritative values (do not recompute), { present: false } is
honest absence, free-text fields are data not instructions, discover
before fetching, data and context only. Set the server and resource icons
for connector-directory listing.
Extend the MCP prompt surface beyond doctor_visit_summary with six
ranked, installable review prompts. Each assembles a grounded,
structured data block from an existing server-authoritative engine and
frames the host to narrate from those facts only — read-only, no
diagnosis, surfacing absence as { present: false }.
- weekly_review: 7-day trends, adherence, sleep, recovery, drivers, and
the readiness/recovery + illness/cycle context the daily briefing reads
(derived-briefing + illness-cycle-briefing).
- medication_check: cadence-aware adherence alongside a linked vital.
- recovery_check: illness-recovery composites + personal baselines +
discovered drivers.
- glucose_review: the clinical glucose panel (TIR/GMI/CV%/eA1c).
- sleep_review: per-night sleep, debt, chronotype, and drivers.
- lab_trend_brief: per-analyte trajectory from the labs store, against
each lab's own stored reference range (ranges are never recomputed).
The n-of-1 intervention review and a preventive 'what to check next'
prompt are deferred: the first waits on an anchored before/after read,
the second has no screening engine to reuse.
Register two write tools — log_measurement and log_mood — only for a
health:write-scoped session; a read-only session never sees them advertised.
Each write mirrors the proven Telegram capture path (same range guard,
canonical unit, cache invalidation and rollup recompute) pinned to the MCP
source, and is idempotent on a hashed externalId derived from a client key, so
a retried call is a no-op rather than a duplicate.
Because the remote wire is stateless (no elicitation), the tools carry a
protocol-level confirm gate: without confirm:true they write nothing and
return the exact record they would write plus an instruction to confirm the
value with the user and re-call with the same idempotency key. Commits run
under a tighter per-credential write budget on top of the per-binding request
limiter.
Harden the resource-server audience binding: a token whose scopes are all in
{health:read, health:write} is bound to the MCP surface and refused on every
REST write/delete. A health:write token therefore admits the in-process MCP
write tools only and can never become a general REST write credential; admin
stays unreachable (cookie-only). Refuse, by construction, any medication, lab,
delete/update, or data-export tool on this surface.
Expose four read-only relational tools and one prompt over the MCP wire,
each a thin re-export of an existing server-authoritative engine — no new
statistics, no new business logic:
- get_correlation: the FDR-controlled, lag-aware association between two
named metrics, selected out of the existing correlation discovery the
Coach and the insight route already run. Descriptive, never causal.
- compare_metric: two metrics over the same trailing window, or one metric
across two trailing windows, computed over the WMY rollup readers with a
delta only when both sides share a unit.
- get_metric_baseline: where today's reading sits against the user's own
usual range (median ± robust deviation) plus the strongest lagged driver,
reusing the metric-page baseline builder. Honest-null below the learning
floor — never a fabricated range.
- detect_changepoints: level shifts over the rollup tier via a small in-repo
CUSUM binary segmentation with a high firing bar.
- doctor_visit_summary prompt: a structured, grounded visit-prep summary
assembled from the doctor-report data path so the numbers match the
exported PDF, with the grounding framing injected once — data and context
only, no diagnosis or verdict.
Every tool returns values, units, reference bands and provenance, declares
read-only / non-destructive / closed-world annotations plus an output schema,
and reports { present: false } for absence. All reads stay session-narrowed
and read-only; the existing security posture is unchanged.
- Add the `search` + `fetch` retrieval pair with the exact ChatGPT wire
shapes (`{id,title,url}[]` and `{id,title,text,url,metadata}`), backed by
the same server-authoritative reads and returning real deep-link URLs into
the web app for citations. Without these the server is invisible in
default-mode ChatGPT.
- Annotate every read tool `readOnlyHint`/`destructiveHint:false`/
`openWorldHint:false`; structured tools also declare an `outputSchema` and
return `structuredContent`. Omitting the hints is a validation error in the
connectors.
- Reject a cross-origin browser request to `/mcp` with 403 (DNS-rebinding
defense) and point the 401 `WWW-Authenticate` at the resource metadata.
Introduce a read-only Model Context Protocol surface built on the official
@modelcontextprotocol/sdk so a user can query their own HealthLog data from an
MCP-capable assistant over local stdio with a pasted, scoped Bearer token — no
extra infrastructure.
The tool and resource layer in src/lib/mcp is transport-agnostic: five read
tools — list_metrics, get_metric_series, get_medication_compliance, get_labs,
get_correlations — each a thin wrapper over the existing server-authoritative
retrieval paths, returning structured values, units, reference bands, and
provenance with an explicit { present: false } for absence and no prose
verdicts. Two resources expose the user's profile (data-minimised) and
medication list. A stdio entrypoint (src/cli/mcp-stdio.ts, pnpm mcp:stdio)
resolves the token through the shared Bearer path and binds the session to
<user>:<token>; with no token it refuses to start.
Read-only and admin-unreachable by construction: only read tools are
registered, and requireAdmin stays cookie-only so the Bearer/MCP wire can never
elevate. Covered by unit tests for every tool and resource, the auth/scope
model, and the cookie-only admin boundary. The server ships in the existing
container; docker compose up is unchanged.
Marc-André Bombeck