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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds that the scope widens to the full library plus the board's images, which is useful behavioral context. It says nothing about pagination, ordering, or how many images come back, so the description goes only modestly beyond the annotations.

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 compact sentences, front-loaded with what the tool returns and followed by how the url is consumed. No filler, though the three use-case examples in the second sentence could be tightened.

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?

There is no output schema, and the description only gestures at the return value ('Die url'), without describing the record shape (ids, names, types) an agent needs to pick an image. For a read-only listing tool this is an adequate but incomplete definition.

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 board_id is already documented, but the description adds the default semantics the schema omits: without board_id you get the library across all boards, and a board's images are included on top. That clarifies the additive behavior rather than just restating the parameter.

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?

The description names the resource precisely: the teacher's images, split into the global library ('für alle Boards') and per-board images. It's clear what the tool returns and how the two scopes differ. It doesn't explicitly contrast itself with list_files or save_image, so a sibling distinction is left implicit.

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?

It gives downstream usage context — the returned url feeds add_widget (image.url, thought.image), a board background, or a vocabulary card — which implicitly tells the agent when this tool is the right first step. However, it never states when to prefer it over list_files/save_image or what to do if no images exist.

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