# PPL Free Ground School

> Free FAA private-pilot ground school: source-cited answers, lessons and practice questions.

- name: com.pplfree/ground-school
- version: 1.0.0
- connection class: R0 (autonomous)
- trust: 82/100 flags: no-repository
- quality: 91/100 (strong)
- owner: not claimed
- descriptor: https://api.protogrid.dev/v1/servers/com.pplfree%2Fground-school
- tools: https://api.protogrid.dev/v1/servers/com.pplfree%2Fground-school/tools

**An agent can connect right now, no human step.** Remote endpoint, no authentication, reachable on the last probe.

## Connection (mcpServers)

```json
{
  "mcpServers": {
    "ground-school": {
      "type": "http",
      "url": "https://pplfree.com/mcp"
    }
  }
}
```


## Trust

- hygiene: 80
- liveness: 98
- freshness: 100
- provenance: 55
- drivers: +dns-namespace +website +reachable +uptime-94% +updated-24d-ago -no-repository
- Derived from observable signals (official registry feed and our own credential-free probes); no code audit performed.

## Quality 91/100 (strong)

### protocol: 75 (weight 25)

- warn `protocol.modern`: newest supported version is 2025-06-18; 2026-07-28 not supported, older versions are deprecated until 2027-07-28
- n/a `protocol.stateless`: only applies to 2026-07-28 servers
- pass `protocol.transport`: streamable HTTP
- n/a `protocol.list_ttl`: only applies to 2026-07-28 servers

### authorization: n/a (weight 15)

- n/a `auth.prm`, `auth.as_metadata`, `auth.cimd`: no remote uses OAuth
- n/a `auth.secret_in_url`: no templated URL

### tool hygiene: 100 (weight 30)

- pass `tools.descriptions`: every tool has a description
- pass `tools.description_length`: descriptions are concise
- pass `tools.schemas`: every tool has an object input schema
- pass `tools.annotations`: 5 of 5 tools declare readOnlyHint or destructiveHint
- pass `tools.directory_hints`: every tool declares readOnlyHint, destructiveHint, idempotentHint and openWorldHint
- pass `tools.token_cost`: about 1,300 tokens to load every tool
- pass `tools.api_dump`: tools are not a one-to-one API dump

### stability: 100 (weight 15)

- pass `stability.changes`: 2 tool changes in 30 days
- pass `stability.rug_pull`: no tool changed its meaning under the same name

### dependencies: n/a (weight 15)

- n/a `deps.known_vulns`, `deps.mcp_sdk_version`, `deps.resolvable`: no npm or PyPI package

- tools: 5, about 1,300 tokens to load them all
- tool set hash: d364b55cdb246aa94fc12b3bf61f5c57
- tools last changed: 2026-09-27T01:15:12.016Z
- badge: [![protogrid quality](https://protogrid.dev/badge/com.pplfree/ground-school.svg)](https://protogrid.dev/servers/com.pplfree/ground-school)
- Checks run on what our credential-free, read-only probes observe; tools are never called and no code audit is performed.

### Tool changes

- 2026-09-27 `check_answer` added
  - Grade the user's answer to a practice question from get_practice_question. Use this when the user replies with their choice (for example "B" or "I think it is C"): pass the question_id and their choice. Returns whether the answer is correct, the correct choice, why each choice is right or wrong, and the FAA citations. It also returns save_progress_url, a pplfree.com link where the user can save the answers from this chat to their study progress on that site, and save_token: pass it back as previous_token on the next check_answer call so one link collects every answer in the chat (up to 20, valid for 7 days). Nothing is stored unless the user opens the link.
- 2026-09-27 `get_practice_question` changed (description)
  - before: Return private-pilot practice questions written for this course in the style of the FAA knowledge test (not actual FAA test questions), each with its answer choices, its topic, a question_id and a link to try it on pplfree.com. The correct answer is withheld by default so the user can attempt the question first. Once the user has answered, call again with that question_id and reveal_answer: true to get the correct choice and an explanation of why each choice is right or wrong. Use this when the user wants to be quizzed, asks for practice or test questions, wants to check their understanding of a topic, or is preparing for the FAA private-pilot knowledge test. Optionally scope it to a topic.
  - after: Return private-pilot practice questions written for this course in the style of the FAA knowledge test (not actual FAA test questions), each with its answer choices, its topic, a question_id and a link to try it on pplfree.com. The correct answer is withheld by default so the user can attempt the question first. Once the user has answered, call check_answer with that question_id and their choice to grade it (or call this tool again with the question_id and reveal_answer: true to show the answer without grading). Use this when the user wants to be quizzed, asks for practice or test questions, wants to check their understanding of a topic, or is preparing for the FAA private-pilot knowledge test. Optionally scope it to a topic.

Full history: https://api.protogrid.dev/v1/servers/com.pplfree%2Fground-school/changes

## Remotes

- https://pplfree.com/mcp (streamable-http, auth none, reachable true, uptime30d 0.9431818)

## Packages

_none_

## Tools (5)

- `check_answer`: Grade the user's answer to a practice question from get_practice_question. Use this when the user replies with their choice (for example "B" or "I think it is C"): pass the question_id and their choice. Returns whether the answer is correct, the correct choice, why each choice is right or wrong, and the FAA citations. It also returns save_progress_url, a pplfree.com link where the user can save the answers from this chat to their study progress on that site, and save_token: pass it back as previous_token on the next check_answer call so one link collects every answer in the chat (up to 20, valid for 7 days). Nothing is stored unless the user opens the link.
- `get_lesson`: Fetch one full ground-school lesson: its summary, why it matters in flight, the learning objectives it covers, and a link to read it. Use this after search_faa_knowledge when the user wants the whole topic rather than a single answer, or when they ask to study or learn a subject properly. Call list_curriculum first if you do not already have a lesson key.
- `get_practice_question`: Return private-pilot practice questions written for this course in the style of the FAA knowledge test (not actual FAA test questions), each with its answer choices, its topic, a question_id and a link to try it on pplfree.com. The correct answer is withheld by default so the user can attempt the question first. Once the user has answered, call check_answer with that question_id and their choice to grade it (or call this tool again with the question_id and reveal_answer: true to show the answer without grading). Use this when the user wants to be quizzed, asks for practice or test questions, wants to check their understanding of a topic, or is preparing for the FAA private-pilot knowledge test. Optionally scope it to a topic.
- `list_curriculum`: List the ground-school curriculum: modules and the published lessons in each, with their keys. Use this to orient yourself before get_lesson, to answer "what does the course cover", or to help a user plan what to study next.
- `search_faa_knowledge`: Answer a US private-pilot (FAA) ground-school question from a source-cited curriculum. Use this whenever the user asks about FAA regulations, airspace, VFR weather minimums, weight and balance, aerodynamics, aircraft systems, navigation, weather theory, human factors, or private-pilot certification requirements. Returns short passages, each with the FAA citation it came from (e.g. "14 CFR 91.155", "PHAK Ch. 15") and a link to the lesson. Cite those labels in your answer.