Logospell

extend_image_set

Add more subjects to a set made with generate_image_set. The new batch is generated exactly as the set was - the same style text and style references, with the background (a color or transparent), size, format, quality, margin, sizing and file size limit of the batch you name - so a set grows past the 16-subject limit of one call without drifting; only the subjects are new. A set made with style references is sent them again, and only them; a set made from text alone is sent up to 3 images from its first batch, so the new subjects are drawn like the rest of the set. The new batch joins the set: listings show the batches together, and the whole set's download window restarts. Each call costs what a generation of the set costs: 1 credit per call. Run generation calls sequentially, never in parallel - only one generation runs at a time per API key.

Subjects that do not describe distinct, drawable subjects are refused before anything is generated or charged. To change the style, the size, or anything else, start a new set instead; to change only how an existing set is delivered, use edit_set.

IMPORTANT - subject description rules:

Subject descriptions should describe WHAT to depict, not where to position it.
Each image is ONE isolated subject, not a scene. Describe the subject with its pose or action and anything it directly holds, rides, or interacts with, but not the surrounding setting, environment, landscape, or sky. For composed scenes (a figure set within an environment), use generate_illustration_set instead.
Do not use size words (large, tiny, small, etc.) on the overall image subject (e.g. 'a large elephant', 'a tiny mouse') - all images are produced at the same size. Size words on details within the image are fine (e.g. 'a plate with a small insignia').
Subjects must be distinct: entries that differ only in case, punctuation, or spacing count as the same subject and the call is rejected. Explicit filenames must be distinct too (a different extension alone is not distinct).
Maximum 16 subjects per call.
If the subject check returns a suggested cleanup, show the user the specific changes and get their confirmation, then resubmit the approved prompt with validation set to "skip" so it generates exactly as approved (resubmitting without "skip" re-runs the check and may return further suggestions). See the validation parameter for when to use "skip" and "auto-apply".
If a "Rate limit exceeded" error is returned, wait the suggested number of seconds before retrying. Do not retry immediately.
Showing the result: as soon as the call returns, show the user every delivered image before you put them to use, then keep working without waiting for a reply (unless the user asked to review first), so they can ask for a change before anything is built on them. Show each image exactly as delivered, as its own file: the files are the product, and their exact size, margin and background are what the user asked for. Never present a new image made from them, even to check them; it hides all three. Files on disk or a link in your context are not delivery. Where you can open files on the user's machine, open the extracted index.html with the host's file opener; it shows each image at its delivered size with its dimensions. Where you can attach files to your reply, attach each delivered file as it is (attaching is not inspecting). Otherwise give the online viewer link and the zip link. Show every image unless the user asked for only some, and say in one line what you left out; if you can show none, say the set was made but you could not show it, and give the viewer link.

Input Schema

Name	Required	Description
`subjects`	Yes	Either a list of subject names (e.g. ["home", "search"]) or objects with description and filename (e.g. [{"description": "compass rose", "filename": "overview.webp"}]). Each subject must name a drawable subject and be distinct: entries differing only in case, punctuation, or spacing are rejected as the same subject. A subject with no Latin letters or numbers (a name written entirely in another script) needs the object form with a filename, since delivered files are named in ASCII. Write each subject as plain text, with no list marker such as "1." or "-" in front, no square brackets, and no invisible characters.
`unpackTo`	No	Path on the caller's local filesystem where the generated files should be saved. The server does NOT write here. After this call returns, you (the calling client) must download images.zip from the returned zip URL, extract it to this path yourself, then report the path to the user. Make the download your immediate next action when the result arrives, before any commentary; the download URL expires (the result states when).
`generation`	Yes	The id of any batch in the set to extend: the random segment of its download URL (.../download/<id>/images.zip), also returned by list_recent_generations. The new batch is generated exactly as that set: the same tool, style text and style references, and the named batch's background, size, format, quality, margin, sizing and file size limit.
`validation`	No	How to handle the automatic subject check before generating. One of: suggest (the default) - if the new subject descriptions need cleanup for a consistent set, the cleaned version is returned as a suggestion for you to review before any image is generated; skip - skip the cleanup suggestions and generate exactly as given (the non-drawable-content and repeated-subject rejection rules above still apply; no mode skips them), set this when resubmitting a prompt you already revised from a previous suggestion (so your approved wording is used as-is and not re-checked, which avoids further suggestions) or when you are confident the prompt is already clean; auto-apply - if cleanup is needed, apply it and generate in one step without returning a suggestion. Omit for the default.

Output Schema

Name	Required	Description
`style`	No
`format`	No	The delivered image format.
`images`	No	The generated images: each one's file name inside the zip, its subject, and its pixel width and height.
`zipURL`	No	Download URL for the zip of generated images. Time-limited; expiresAt states the deadline.
`unpackTo`	No	The caller-supplied local extraction path, echoed back.
`expiresAt`	No	When the download URL expires.
`remaining`	No	Credits remaining after this call.
`background`	No	The background color used, or transparent.
`manifestURL`	No
`rejectedStyle`	No	Present only when the request was rejected because the style does not appear to describe a visual style: the submitted style text. No generation ran and nothing was charged; revise the style (or drop it and use styleReferences) and resubmit.
`suggestedStyle`	No	Present only on a validation suggestion: the cleaned style text, for review. An empty string means the cleanup removed the style entirely (nothing in it was usable as a style) - replace it, or use styleReferences. Absent when the style was not checked (references only, or an extension). No generation ran and nothing was charged.
`rejectedSubjects`	No	Present only when the request was rejected because some subjects do not appear to name distinct, drawable subjects: the exact rejected entries. No generation ran and nothing was charged; revise or remove these subjects and resubmit.
`suggestedSubjects`	No	Present only on a validation suggestion: the cleaned subject list, one entry per image. Adopt these, or resubmit your own wording with validation set to skip.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 22, 2026

changedInput schema / properties / subjects / description

Previous value: -"Either a list of subject names (e.g. [\"home\", \"search\"]) or objects with description and filename (e.g. [{\"description\": \"compass rose\", \"filename\": \"overview.webp\"}]). Each subject must name a drawable subject and be distinct: entries differing only in case, punctuation, or spacing are rejected as the same subject. A subject with no Latin letters or numbers (a name written entirely in another script) needs the object form with a filename, since delivered files are named in ASCII. Subject text can use only letters, numbers, dashes, spaces, and apostrophes, and must start and end with a letter or number."New value: +"Either a list of subject names (e.g. [\"home\", \"search\"]) or objects with description and filename (e.g. [{\"description\": \"compass rose\", \"filename\": \"overview.webp\"}]). Each subject must name a drawable subject and be distinct: entries differing only in case, punctuation, or spacing are rejected as the same subject. A subject with no Latin letters or numbers (a name written entirely in another script) needs the object form with a filename, since delivered files are named in ASCII. Write each subject as plain text, with no list marker such as \"1.\" or \"-\" in front, no square brackets, and no invisible characters."

Changed5 schema fields changedOct 16, 2026

changedInput schema / properties / generation / description

Previous value: -"The id of any batch in the set to extend: the random segment of its download URL (.../download/<id>/images.zip), also returned by list_recent_generations. The new batch is generated exactly as that set: the same tool, style text and style references, and the named batch's background, size, format, quality, margin and sizing."New value: +"The id of any batch in the set to extend: the random segment of its download URL (.../download/<id>/images.zip), also returned by list_recent_generations. The new batch is generated exactly as that set: the same tool, style text and style references, and the named batch's background, size, format, quality, margin, sizing and file size limit."

addedOutput schema / properties / images / items / properties / bytes

Added value: +{
+  "description": "The image file's size in bytes.",
+  "type": "integer"
+}

addedOutput schema / properties / images / items / properties / maskLevels

Added value: +{
+  "description": "Under a file size limit (maxKB): how many transparency levels this image kept; 256 is exact.",
+  "type": "integer"
+}

addedOutput schema / properties / images / items / properties / overBudget

Added value: +{
+  "description": "Under a file size limit (maxKB): true when this image is still over the limit at the lowest step (quality 70, or the set's own when that is lower).",
+  "type": "boolean"
+}

addedOutput schema / properties / images / items / properties / quality

Added value: +{
+  "description": "Under a file size limit (maxKB): the quality this image was delivered at.",
+  "type": "integer"
+}

Changed7 schema fields changedOct 12, 2026

changedOutput schema / properties / background / description

Previous value: -"The background color used; absent for transparent sets."New value: +"The background color used, or transparent."

changedOutput schema / properties / images / description

Previous value: -"The generated images: subject name, filename inside the zip, and pixel width and height."New value: +"The generated images: each one's file name inside the zip, its subject, and its pixel width and height."

addedOutput schema / properties / images / items / properties / description

Added value: +{
+  "description": "The subject, variation or scene this image was made from, as the call gave it.",
+  "type": "string"
+}

addedOutput schema / properties / images / items / properties / filename / description
```
Added value: +"The image's file name inside the zip."
```
removedOutput schema / properties / images / items / properties / name
```
Removed value: -{
-  "type": "string"
-}
```

changedOutput schema / properties / images / items / required

Previous value: -[
-  "name",
-  "filename"
-]New value: +[
+  "filename",
+  "description"
+]

changedOutput schema / properties / suggestedStyle / description

Previous value: -"Present only on a validation suggestion: the cleaned style text, for review. An empty string means the cleanup removed the style entirely (nothing in it was usable as a style) - replace it, or use styleReferences. Absent on refs-only requests. No generation ran and nothing was charged."New value: +"Present only on a validation suggestion: the cleaned style text, for review. An empty string means the cleanup removed the style entirely (nothing in it was usable as a style) - replace it, or use styleReferences. Absent when the style was not checked (references only, or an extension). No generation ran and nothing was charged."

AddedOct 10, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Goes far beyond the annotations: discloses cost (1 credit per call), a serialization constraint (never run generation calls in parallel, one generation per API key), rate-limit retry behavior, that subjects are validated and refused before charging, that the whole set's download window restarts, and that the zip URL expires. Annotations only say non-readonly, non-idempotent, open-world.

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

Conciseness3/5

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

Front-loaded with the core purpose and cost, which is good, but the body is very long and the 'Showing the result' block runs several sentences with parenthetical restatements ('attaching is not inspecting', 'files on disk or a link in your context are not delivery') that could be tightened. The subject-rule bullets and delivery instructions together dominate the description.

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 paid, non-idempotent generation tool with an output schema, the description covers everything an agent needs: inheritance semantics, validation flow, cost, concurrency limits, failure modes, and how to present deliverables. Return format is correctly left to the output schema.

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 100%, so baseline is 3; the description adds real meaning by documenting the three validation modes ('suggest'/'skip'/'auto-apply') and the exact resubmit-after-suggestion workflow, which the schema leaves as an unspecified string. The generation parameter's 'any batch id from the set' semantics are also clarified beyond the schema.

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 opening sentence states a specific verb (add subjects) and resource (an existing set made with generate_image_set), and explicitly scopes what is inherited (style, background, size, format) versus what is new (only the subjects). It is immediately distinguishable from generate_image_set, extend_character_set, extend_illustration_set, and edit_set.

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?

Explicit routing rules are given: to change style or size, 'start a new set instead'; to change delivery only, 'use edit_set'; for composed scenes, 'use generate_illustration_set instead'. The 16-subject overflow rationale explains the primary when-to-use condition.

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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