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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuine behavioral context beyond them: results are newest-first, the gallery is populated only via the editor, and image names are human-authored and should be treated as data (a prompt-injection caution). It does not discuss pagination or truncation behavior for the list itself.

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?

The purpose, scope, and key facts are front-loaded in the first clause, and most sentences carry unique information (ordering, id linkage, contact sheet, no-upload constraint, name caveat). It runs slightly long and the phrasing around the contact sheet and the id/imageId link is a touch convoluted, but nothing is pure filler.

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?

An output schema exists, so return-value documentation is optional, yet the description still usefully names the fields and their ordering. Combined with the upload-path explanation, id semantics, and param intent, an agent has enough to call the tool correctly; only pagination/truncation behavior for long galleries is left unaddressed.

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 description coverage is 100%, so the baseline is 3, and the description earns a point above it by explaining what the 'image' flag is for in intent terms ('add a contact sheet, to see which picture is which') rather than merely restating the schema. 'limit' and 'query' get no additional semantic detail in the description.

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?

Names a specific verb and resource ('List the pictures in the user's image gallery'), defines the resource precisely (what was uploaded to livediagram, e.g. screenshots), and states the ordering (newest first) and returned fields (id, name, width, height, size, when). No sibling tool lists images, and the description makes the image gallery distinct from diagrams/documents/sheets.

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?

Tells the agent that pictures arrive only through the editor (upload/paste/drop) and that 'there is no upload tool' — an explicit negative that prevents a wrong tool search. It also explains the relationship route (an image element's imageId takes a listed id), giving clear context, but stops short of naming an alternative tool or an explicit when-not-to-call condition, largely because no alternative exists.

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