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

Annotations already cover safety (readOnlyHint, idempotent, non-destructive, not open-world), and the description adds substantial extra context: the work happens on collager.ai, the user uploads and picks a style, the preview is watermarked, it takes minutes, and 100-2000 photos is the sweet spot. This tells the agent the tool itself performs no heavy work and what the downstream flow looks like.

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 sentences, front-loaded with the core action ('Gives the link where the user builds a photo mosaic'), followed by the mechanics and then the trigger. Efficient with no filler, though the example list could be trimmed without loss.

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 zero-required-parameter, annotation-covered tool with no output schema, the description covers the return value (a link), the downstream workflow, photo-count guidance, and the trigger condition. Nothing essential to calling it correctly is missing.

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?

Only one optional parameter (occasion) with 100% schema description coverage, so the schema already fully documents it. The description's occasion-like examples (wedding, team, school year) loosely align but never explain the parameter's role in tailoring tips, adding nothing beyond the schema.

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 concrete verb and resource: it returns the link where the user builds a photo mosaic, then defines what a photo mosaic is (one main photo recreated from many small photos). It does not explicitly name the sibling it contrasts with (make_shape_collage), so it falls just short of full sibling differentiation.

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 final sentence gives a clear trigger: 'Use when the user wants a photo mosaic or a picture made of many photos.' There is no explicit when-not or named alternative (e.g., shape collage vs photo mosaic), but the usage context is unambiguous.

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