Velven

Publish a space

publish

Publish a browser game, world, tool or wonder on Velven's hosting, from one HTML page or a small set of files (3 MB in all). Signed in: a private preview by default, or with prod: true the next live version, live on its Velven page within seconds. Not signed in: an unlisted page, live the same way, returned with a claim token that keeps it. A new space needs title, type and devices from the person. To update a space pass space (signed in) or claim (not signed in).

Input Schema

TableJSON Schema

Name	Required	Description
`sdk`	No	Add Velven's SDK script to the entry page. Default true.
`spa`	No	Serve the entry page for any unknown path (a single-page app).
`clip`	No	The video the tile plays on hover, without sound. Give the path of one of the files sent: an MP4 or WebM, up to 3 MB and 5 to 10 seconds long. Velven then records no clip of its own. Without a thumbnail, the clip's first frame is the picture. It must show the space itself. A clip outside that length is refused. If the file doesn't say its length, Velven measures it once live. It keeps the first 10 seconds of a longer clip, and drops a shorter one. A later version that names neither keeps the space's.
`html`	No	A whole page as one HTML string, published as index.html.
`prod`	No	Go live on the space's Velven page instead of making a preview. Signed in only. Default false.
`type`	No	What it is. Required for a new space.
`claim`	No	The claim token of an unlisted page: publishes its next version, or claims it when signed in.
`entry`	No	The page that opens first, if not index.html.
`files`	No	Files by relative path: text as a string, binary as { "base64": "..." }. Must include the entry page (index.html unless entry says otherwise). A velven.json, a dotfile, a dot-folder or node_modules, in any folder, is left out (never published; the result names the first 10 and counts the rest): send velven.json's settings as this tool's fields.
`space`	No	Publish a new version of this space (yours, signed in).
`title`	No	The space's name. Required for a new space.
`engine`	No	What it draws with, if one of these.
`devices`	No	Where it can be played. Required for a new space.
`how_made`	No	How it was made, in the creator's words.
`thumbnail`	No	The picture on the space's tile. Give the path of one of the files sent: a JPEG, PNG or WebP, up to 2 MB and 4096 pixels on each side. It's used as soon as the version is live, and Velven takes no picture of its own. It must show the space itself.
`description`	No	One line under the name.

Output Schema

TableJSON Schema

Name	Required	Description
`space`	Yes	The space's slug.
`terms`	No	The Terms line to show the person (no account).
`reason`	No	Why it was refused, naming the file when it was one.
`status`	Yes	The version's status: preview, publishing (waiting on Velven to publish it), live or refused.
`leftOut`	No	Files not published (velven.json, dotfiles, node_modules), the first 10.
`pageUrl`	Yes	The space's page on Velven.
`version`	Yes	The version this publish made.
`claimUrl`	No	Open signed in to claim the page (no account).
`watchUrl`	No	Where to follow the version on Velven.
`expiresAt`	No	When an unlisted page is deleted unless claimed (no account).
`claimToken`	No	The unlisted page's claim token, shown once (no account).
`previewUrl`	No	The private preview, for 24 hours (a preview only).
`leftOutCount`	No	How many files were left out in all.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 28, 2026

changedInput schema / properties / clip / description

Previous value: -"The short muted video its tile plays on hover: the path of one of the files sent, an MP4 or WebM up to 3 MB (five seconds at 480p is right). Velven records no clip then; without a thumbnail, the clip's first frame is the picture. A later version that names neither keeps the space's."New value: +"The video the tile plays on hover, without sound. Give the path of one of the files sent: an MP4 or WebM, up to 3 MB and 5 to 10 seconds long. Velven then records no clip of its own. Without a thumbnail, the clip's first frame is the picture. It must show the space itself. A clip outside that length is refused. If the file doesn't say its length, Velven measures it once live. It keeps the first 10 seconds of a longer clip, and drops a shorter one. A later version that names neither keeps the space's."

changedInput schema / properties / thumbnail / description

Previous value: -"The space's picture on its tile: the path of one of the files sent, a JPEG, PNG or WebP up to 2 MB. It is used from the moment the version is live, instead of a picture Velven takes."New value: +"The picture on the space's tile. Give the path of one of the files sent: a JPEG, PNG or WebP, up to 2 MB and 4096 pixels on each side. It's used as soon as the version is live, and Velven takes no picture of its own. It must show the space itself."

Changed6 schema fields changedSep 28, 2026

addedInput schema / properties / clip

Added value: +{
+  "description": "The short muted video its tile plays on hover: the path of one of the files sent, an MP4 or WebM up to 3 MB (five seconds at 480p is right). Velven records no clip then; without a thumbnail, the clip's first frame is the picture. A later version that names neither keeps the space's.",
+  "type": "string"
+}

changedInput schema / properties / prod / description

Previous value: -"Go live after the safety check instead of a preview. Signed in only. Default false."New value: +"Go live on the space's Velven page instead of making a preview. Signed in only. Default false."

addedInput schema / properties / thumbnail

Added value: +{
+  "description": "The space's picture on its tile: the path of one of the files sent, a JPEG, PNG or WebP up to 2 MB. It is used from the moment the version is live, instead of a picture Velven takes.",
+  "type": "string"
+}

addedOutput schema / properties / reason

Added value: +{
+  "description": "Why it was refused, naming the file when it was one.",
+  "type": "string"
+}

changedOutput schema / properties / status / description

Previous value: -"The version's status: preview, checking (in the safety check) or live."New value: +"The version's status: preview, publishing (waiting on Velven to publish it), live or refused."

changedOutput schema / properties / watchUrl / description

Previous value: -"Where to follow the check."New value: +"Where to follow the version on Velven."

First observedSep 28, 2026

TDQS

A4.8/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only give the generic mutation/openWorld profile; the description adds the genuinely non-obvious behavior – preview-by-default versus going live within seconds, the claim token that keeps an unlisted page, and the 3 MB aggregate size limit. This is real context beyond what the structured fields already say.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the verb and resource, and every sentence carries routing or constraint information with no filler. It is dense to the point of being hard to parse in one pass (nested conditionals crammed into one paragraph), which keeps it off a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 16-parameter, nested-object tool with an output schema and full schema coverage, the description covers the publishing flow, auth modes, update paths and new-space prerequisites. Return values need not be explained because an output schema exists.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3, but the description adds cross-parameter semantics the schema states only locally: the space-vs-claim branch for updating, and the title/type/devices requirements for a new space. It stops short of explaining defaults like sdk or spa, which the schema already carries.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (publish) and resource (a browser game, world, tool or wonder on Velven's hosting), plus scope limits (one HTML page or a small set of files, 3 MB). Reads unambiguously as a deploy/publish operation and is clearly distinct from the read/history siblings my_spaces, versions and rollback.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly routes between modes: signed in defaults to a private preview unless prod: true, unsigned becomes an unlisted page with a claim token, new spaces require title/type/devices, and updates go through either space (signed in) or claim (unsigned). The when-to-use conditions are all stated rather than implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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