---
title: "What a client gets at initialize"
description: "A client launches this server as a subprocess and sends initialize before anything else."
canonical: initialize.html
navigation-title: "Initialize"
---
# What a client gets at initialize
- [The four members](#the-four-members)
- [What the instructions carry](#what-the-instructions-carry)
- [What arrives after](#what-arrives-after)
- [What holds it](#what-holds-it)
- [The initialize result](#the-initialize-result)
- [The prompts](#the-prompts)
- [The tool list](#the-tool-list)
- [The resource template](#the-resource-template)
A client launches this server as a subprocess and sends `initialize` before
anything else. The answer is the first text the model reads from this server.
For most sessions it is also the only text that arrives without a call. A client
that defers its tools sends the model their names alone,
[D-AUD-003](https://github.com/TYPO3/dev-companion/blob/main/decisions/audience/aud-003-the-instructions-carry-the-entry-point-because-the-tool-descriptions-never-arrive.md).
This page shows that answer as the server sends it, and the three lists a client
fetches right after it.
## The four members
- **\`\`protocolVersion\`\`** — the newest revision the stdio transport speaks. A
client that offers a newer one gets this one back rather than a refusal, and
`StdioServerTest` holds that.
- **\`\`capabilities\`\`** — what [Factory](https://github.com/TYPO3/dev-companion/blob/main/src/Server/Factory.php)
declares, which is what the server does: tools, resources, prompts, and the
completion of the two closed arguments of the `commit_message` prompt,
[D-ANS-166](https://github.com/TYPO3/dev-companion/blob/main/decisions/answers/ans-166-initialize-declares-the-capabilities-the-server-honours.md).
Under `extensions` stands the Skills extension, and
[resources/](resources/index.md) says what it adds. No list carries
`listChanged`, because nothing here changes a list while a session runs.
Nothing carries `logging` or `subscribe`, because no log message and no
resource update ever leaves this server.
- **\`\`serverInfo\`\`** — the name, the version, the title, the description and the
site `Factory` declares, and the mark at two optical sizes as `data:`
URIs, because a stdio server has no origin a client could fetch one from.
- **\`\`instructions\`\`** — the statement
[Coverage](https://github.com/TYPO3/dev-companion/blob/main/src/Knowledge/Coverage.php) assembles from
`knowledge/server-scope.json`. The four parts of it are the opening, the
index of which tool answers what, the note under the index and the close.
## What the instructions carry
The instructions open with the first call of any task, because the tool
descriptions are not a channel a deferred session reads. Then they route the
questions a session asks most, name the skill listing, and say that the server
answers in English. The whole of it fits the 2048 characters the recorded client
keeps,
[R-ANS-013](https://github.com/TYPO3/dev-companion/blob/main/requirements/answers/ans-013-the-instructions-fit-what-a-client-keeps.md).
A client cuts past that without a word to either side, so the budget covers
everything assembled, prefix and suffix included.
Three things change the text from one start to the next:
- **A notice in front.** Where the task skills published into the project are
stale, `Installer` puts them back and opens the instructions with one
sentence that says so,
[D-DIS-021](https://github.com/TYPO3/dev-companion/blob/main/decisions/discovery/dis-021-a-stale-publication-is-put-back-where-the-server-starts.md).
- **The exclusion in front of the routing.** Where
`TYPO3_DEV_COMPANION_EXCLUDE_TOOLS` names tools, the instructions say which
are left out and drop every index entry that routed to one,
[R-SCO-009](https://github.com/TYPO3/dev-companion/blob/main/requirements/scope/sco-009-individual-tools-can-be-excluded.md).
Past what the budget holds, the count stands in for the names.
- **The write sentence at the end.** A standalone checkout offers
`typo3_feedback_record`, and the instructions say so in their last sentence.
A project that installed the server as a dependency gets neither the tool nor
the sentence. The page below shows the checkout's form.
## What arrives after
- **\`\`tools/list\`\`** — every tool with its description, its two schemas and its
annotations, which is the whole of [tools/](tools/index.md). A client that
follows the API's guidance defers a list this size. It then searches the list
by name and description when the model names a subject,
[D-AUD-019](https://github.com/TYPO3/dev-companion/blob/main/decisions/audience/aud-019-a-lookups-description-names-the-subjects-it-covers.md).
- **\`\`prompts/list\`\`** — the prompts a user picks by name. `debrief` is there
where the feedback channel is, and nowhere else,
[D-FBK-048](https://github.com/TYPO3/dev-companion/blob/main/decisions/feedback/fbk-048-the-debrief-is-offered-as-a-prompt-where-the-channel-is.md).
- **\`\`resources/list\`\`** and **\`\`resources/templates/list\`\`** — the surface a
user picks from rather than the model calls, which
[resources/](resources/index.md) describes whole.
## What holds it
`bin/cli tools:index` writes everything below the marker, from a session it
runs against `Factory::create()` in its own process. `bin/cli tools:check`
and `ToolSurfaceTest` fail where the page says something else than the server
answers. `StdioServerTest` reads the same answer over stdio. So a count on
this page is what the server answered at the commit that wrote it.
## The initialize result
```json
{
"protocolVersion": "2025-11-25",
"capabilities": {
"completions": {},
"prompts": {},
"resources": {},
"tools": {},
"extensions": {
"io.modelcontextprotocol/skills": {}
}
},
"serverInfo": {
"name": "typo3-dev-companion",
"version": "0.3.0",
"description": "Guides a coding agent through TYPO3 implementation, review and verification with version-bound knowledge and the facts of the project it runs in.",
"icons": [
{
"src": "data:image/svg+xml;base64,…",
"mimeType": "image/svg+xml",
"sizes": [
"16x16"
]
},
{
"src": "data:image/svg+xml;base64,…",
"mimeType": "image/svg+xml",
"sizes": [
"32x32"
]
}
],
"websiteUrl": "https://typo3.github.io/dev-companion/",
"title": "TYPO3 Dev Companion"
}
}
```
The two icon sources stand shortened. Each is one of the signets the site draws,
`images/signet-s.svg` and `images/signet-l.svg`, as base64 in a `data:`
URI.
The fourth member is `instructions`, and it reads:
```text
Start every task with typo3_project_describe. It answers the installation's TYPO3 version, the extensions that are the project's own, the sites it configures, and the commands the repository declares. A check you recommend that the repository does not declare is a wrong answer however sensible it sounds. Then call typo3_task_guide for the workflow the task belongs to. Call it again at the first test, check, commit or shipped file the task did not name. Not every task ends in a patch. It also answers a triage of the backlog, whether a report still reproduces, and what a fix costs. What changed, which branch you are on, and whether a path still exists are yours to read in the checkout.
What to call for what:
- backend markup or a CSS class: typo3_component_lookup with the targetVersion
- a backend icon identifier: typo3_icon_lookup
- a label, added or reworded: typo3_label_lookup with the XLF resource the code at hand uses; a match elsewhere is not reusable
- what a version broke, deprecated or added, on a major you have not built on lately: typo3_changelog_lookup
- the commit message, yours as much as the core's, and its branches: typo3_commit_message_guide
- the whole procedure, not one fact out of it: typo3_rule_lookup with a documentId typo3_project_describe lists
Activate the typo3-* skill in your listing that covers the task: it makes these calls.
targetVersion or the version the server read filters the answers, and a statement that does not hold on every covered line carries its range.
Query this server in English whatever language you speak with the user. Its match is lexical, so a query in another language reaches only the loanwords. Translate the subject before you call, and the answer back.
typo3_server_scope says what it covers, by which tool, and which installation it reads. Every tool here is read-only except typo3_feedback_record, which creates a new markdown feedback under feedback/ and writes nothing else.
```
1,959 characters of the 2,048 a client keeps, `Coverage::INSTRUCTIONS_BUDGET`.
## The prompts
- `commit_message` — Draft a TYPO3 commit message. Turn a summary into the
checked commit-message draft already provided by typo3\_commit\_message\_guide.
Takes `summary`, and `keyword`, `workflow` and `issue` where given.
- `debrief` — Debrief the session that has just finished. Ask a finished
session what this server did for it and what it lacked, and have it record
what it found with typo3\_feedback\_record. Run it after the work, in a message
of its own. Takes nothing.
## The tool list
`tools/list` carries 31 tools. Each entry is the `name`, `title`,
`description`, `inputSchema`, `outputSchema` and `annotations` the
tool's own page under [tools/](tools/index.md) states.
`bin/cli tools:measure` prints what each entry weighs on the wire, and what
all of them weigh together.
## The resource template
- `typo3://skill/{skill}/references/{reference}` — What a TYPO3 task workflow
hands over at a step. What a skill under typo3://skill/ links to: the order
every task starts in, its checklist, and the implementation guide for the
layer it settled on. Read the one its body sends you to, at the step that
sends you.