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 non-schema behavioral context — that the call is free and that rendering is inline/idempotent-ish after an upload — but says nothing about invalid asset IDs or the 50-item cap behavior.

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?

Three short sentences, zero filler, with the core action stated first and the sibling exclusion last. Every sentence carries distinct information.

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?

No output schema exists, but since output is 'images rendered inline' the description adequately conveys the return effect. The remaining gap is parameter provenance: an agent is never told what an asset_id is or where to obtain one, which is significant for a single required-array parameter at 0% coverage.

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 0% for the single required parameter 'asset_ids', and the description never names it or explains where the IDs come from. The phrases 'existing images' and 'earlier results' only loosely imply provenance, so the description fails to compensate for the coverage gap.

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 and resource ('Render existing images inline') and scopes it to a situation. It also explicitly distinguishes itself from a close sibling by declaring it is 'not needed after generate_image', so an agent can separate the two without opening either schema.

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?

Gives explicit positive triggers ('the user asks to see earlier results again or after an upload') and an explicit exclusion ('Not needed after generate_image, whose result is already shown'). This is exactly the when/when-not routing guidance the dimension asks for.

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