# Class Profiles

> Shared contracts for MCP capabilities, so an agent can use a server it has never seen. A standards proposal and working prototype — not a standard, not adopted, and not yet implemented by anyone.

MCP revision `2026-07-28` made tools callable and governable and deliberately left meaning out. It names the multi-server collision and offers prefixing, which identifies *which server said it* rather than what it means; it also requires clients to treat tool annotations as untrusted. A Class Profile fills that seam: a small mandatory Core baseline, optional job-shaped facets that declare what their absence costs, and vendor members that stay visible. Routing is on semantic identity, never on spelling.

Two classes are worked — `calendar` and `operator` — chosen to share as little as possible, because one example cannot show whether a format is domain-specific. Between them: two descriptors and eleven fixture documents holding 31 scenarios. `profile.json` is authoritative; `PROFILE.md` and `SKILL.md` are renderings of it.

## Start

- [README.md](README.md): The problem, the proposal, the two classes, what is real and what is not.
- [EXPLAINER.md](EXPLAINER.md): Why tool search does not solve this, who benefits in what order, what we do not know.
- [AGENTS.md](AGENTS.md): Reading order and the rules that bind an agent.
- [GLOSSARY.md](GLOSSARY.md): Working vocabulary.
- [Website](https://classprofiles.org): Progressive walkthrough and a deterministic native/projected simulation.

## Profiles

- [profiles/calendar/profile.json](profiles/calendar/profile.json): Authoritative descriptor. Six Core verbs; invitations, recurrence, reminders, RSVP, tombstone facets; one vendor member.
- [profiles/calendar/SKILL.md](profiles/calendar/SKILL.md): Self-contained operating instructions.
- [profiles/calendar/PROFILE.md](profiles/calendar/PROFILE.md): Rationale and unsettled design questions.
- [profiles/operator/profile.json](profiles/operator/profile.json): Authoritative descriptor. Four Core verbs over any surface; browser, desktop, screenshot facets.
- [profiles/operator/SKILL.md](profiles/operator/SKILL.md): Self-contained operating instructions with worked calls.
- [profiles/operator/PROFILE.md](profiles/operator/PROFILE.md): Rationale, and what the conformance model cannot reach.

## Design

- [spec/01-concepts.md](spec/01-concepts.md): Classes, profiles, baselines, facets, cards, projections, consumers.
- [spec/02-descriptor.md](spec/02-descriptor.md): Tool declarations, private contracts, defaults, examples, degradation.
- [spec/03-conformance.md](spec/03-conformance.md): Fixture format, runner semantics, Claims, receipts.
- [spec/04-projection.md](spec/04-projection.md): Binding capsules, coverage, passthrough, drift.
- [spec/05-kernel.md](spec/05-kernel.md): Identity, schemas, effects, errors, pagination, negotiation, degradation.
- [spec/06-facets.md](spec/06-facets.md): The facet mechanism.
- [PRIOR-ART.md](PRIOR-ART.md): Related protocols and what each one should constrain here.

## Decisions

- [decisions/0001-mcp-2026-07-28-alignment.md](decisions/0001-mcp-2026-07-28-alignment.md): Alignment to MCP `2026-07-28` — extension identity, card placement, re-issue safety, error split, canonicalization, the Extensions Track route.
- [decisions/0002-the-plug-in-test.md](decisions/0002-the-plug-in-test.md): What belongs in a Core baseline — necessity plus sufficiency.
- [decisions/0003-calendar-core-audit.md](decisions/0003-calendar-core-audit.md): That test applied to Calendar.
- [decisions/0004-capability-is-a-job.md](decisions/0004-capability-is-a-job.md): A capability names a job; a target space is a facet.
- [research/mcp-spec/2026-07-28-capture.md](research/mcp-spec/2026-07-28-capture.md): Quoted evidence from the MCP revision.

## Evidence

- [research/discovery/FINDINGS.md](research/discovery/FINDINGS.md): What 300 MCP services declare — zero annotations across 9,390 members, 894 spellings for one primitive, three retrieval arguments under eleven names, and why names do not carry function.
- [research/discovery/README.md](research/discovery/README.md): Cohort construction and the two limits that bound every conclusion.
- [research/discovery/DATA-NOTICE.md](research/discovery/DATA-NOTICE.md): Provenance, rights, and interpretation limits.
- [Dialects page](https://classprofiles.org/dialects/): Measured vocabulary divergence, with receipts.
- [Research notebook](https://classprofiles.org/research/): The evidence in accessible form.

## Implement and contribute

- [guides/build-a-server.md](guides/build-a-server.md): Implement a profile directly.
- [guides/wrap-a-server.md](guides/wrap-a-server.md): Project an existing server through a binding capsule.
- [CONTRIBUTING.md](CONTRIBUTING.md): What helps most, change rules, local commands, delivery.
- [LICENSE](LICENSE) · [NOTICE](NOTICE): Apache-2.0 and provenance.