set_agent_avatar_from_urlUpload a custom avatar photo (JPG, PNG or GIF, ≤5 MB) from a public image URL or base64. Replaces the preset face. Free.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Agent id (UUID) — from list_agents | |
| image_url | No | Public https URL of the image | |
| image_base64 | No | Base64 or data: URL of the image (use instead of image_url) |
Changes observed during successful MCP inspections.
Input schema / properties / id / descriptionAdded value: +"Agent id (UUID) — from list_agents"Input schema / properties / image_base64Added value: +{
+ "description": "Base64 or data: URL of the image (use instead of image_url)",
+ "type": "string"
+}Input schema / properties / image_url / descriptionPrevious value: -"Publicly reachable HTTPS image URL"New value: +"Public https URL of the image"Input schema / requiredPrevious value: -[
- "id",
- "image_url"
-]New value: +[
+ "id"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does disclose useful behavior: it overwrites the preset face, accepts only JPG/PNG/GIF up to 5 MB, and costs nothing. It omits permission requirements, reversibility, and what happens on invalid input or failed fetch, which matter for a mutation tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two tight sentences with the core action and constraints front-loaded; every clause (formats, size, source options, replacement effect, cost) carries information and nothing is padded.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a three-parameter, fully documented, non-destructive-setup tool with no output schema, the description covers format, size, source, and replacement semantics adequately. Only permission and failure-mode context is missing, which is a minor gap given schema completeness.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so baseline is 3, and the description adds genuinely new semantics beyond the schema: allowed image formats, the 5 MB cap, and the either/or choice between URL and base64 sourcing. It still doesn't clarify the id source, but the schema already points to list_agents.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (upload a custom avatar photo) and resource (agent's avatar), plus concrete format and size constraints. It doesn't explicitly distinguish itself from the sibling set_profile_avatar, so an agent must infer the agent-vs-user distinction from the 'id' parameter.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies usage (supply a URL or base64 to replace the preset face) but never states when to call this versus update_agent or set_profile_avatar, nor any prerequisites such as needing an existing agent id. The 'Free' note gives a mild cost signal but no decision guidance.
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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