GravityPort

stack_create

Group two or more saved assets into a new stack, with an optional name and cover asset. Use it to organize GravityPort assets; remove any already-stacked asset first.

Instructions

Group two or more saved assets into a new stack, the same as stacking a selection in the GravityPort app. coverAssetId defaults to the first asset. name (optional, at most 80 characters) is the stack's display name. An asset can belong to only one stack: if any asset is already in a stack the call fails with ASSET_ALREADY_STACKED and nothing changes; take it out with stack_remove_assets first. To show the same image in several stacks, copy it with asset_duplicate and stack the copy. Archived assets cannot be stacked.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "assetIds": "<assetIds>"
    },
    "name": "stack_create"
  }
}

Input Schema

Name	Required	Description	Default
`name`	No
`assetIds`	Yes
`coverAssetId`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.11Nov 11, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description goes well beyond by disclosing transactional behavior ('nothing changes' on failure), the specific error code ASSET_ALREADY_STACKED, and the one-stack-per-asset invariant. These are exactly the mutation-side facts an agent needs and that annotations cannot express.

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

Conciseness5/5

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

Four tight sentences front-loaded with the core action, then defaults, then failure/alternative paths. Every clause carries actionable information; nothing is padding or restated from structured fields.

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

Completeness4/5

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

For a three-parameter mutation with no output schema, the description covers preconditions, defaults, and failure recovery thoroughly. The one omission is the return value — whether the caller receives a new stack ID to chain into stack_get or stack_add_assets — which an agent would have to discover empirically.

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 coverage is 0%, so the description must carry parameter meaning and largely does: it supplies the 'two or more' minimum for assetIds (not in the schema), states coverAssetId defaults to the first asset, and marks name as optional. The name length limit merely restates maxLength=80, and it never says whether assetIds are IDs or paths, which leaves a small gap.

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?

The description opens with a specific verb and resource: 'Group two or more saved assets into a new stack,' and anchors it to a familiar user action in the GravityPort app. It distinguishes itself from stack_add_assets by specifying a NEW stack, and names stack_remove_assets and asset_duplicate as related operations, so an agent can place it correctly without opening sibling schemas.

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?

It gives an explicit precondition (each asset may belong to only one stack), the exact remedy when that fails (call stack_remove_assets first), and the workaround for the multi-stack case (duplicate with asset_duplicate and stack the copy). It also states a hard exclusion — archived assets cannot be stacked — which is precisely the kind of when-not guidance that prevents wasted calls.

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