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

Annotations already declare readOnly/idempotent/non-destructive/non-open-world, yet the description adds substantial context beyond them: max 1280px width, the returned metadata line (file name, size, licence, source, page, credit line), one photo per call, file persistence in conversation, and that this server does not edit images. This is exactly the added behavioral value the dimension rewards.

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?

Front-loaded with the core action and outcome, and most sentences carry distinct information (output contents, resolution, persistence, licensing scope). It is somewhat long at five paragraphs for a one-parameter tool, with mild redundancy around not needing to resend the photograph.

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?

With no output schema, the description fully compensates by enumerating the returned image and its accompanying metadata line, per-call cardinality, and licence/credit applicability. An agent has everything needed to call it and interpret the result.

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% and the schema itself already explains the UUID format and the critical rule to use photo_id rather than a rank. The description only restates that the photo is identified by its photo_id, adding little beyond the structured field, so the baseline 3 applies.

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: returns one photograph from an earlier Pexafy result as an image file, identified by photo_id. It explicitly distinguishes itself from the retrieval-by-link flow and from search siblings (search_photos, get_grid_selected_photos) by noting the link points to the image while this tool returns the image itself.

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 when-to-use cases (place in a document, slide or post; attach, send, download; crop, caption or edit) and an explicit when-not boundary (a photograph already visible on the grid needs no file). The alternative behavior is named rather than left to inference.

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