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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=false), and the description adds genuinely useful behavior beyond them: partial-update semantics, the four-angle cap, removal by index, and clearing semantics (empty string clears placementNotes, empty feature list hands detection back to automatic). It does not mention auth requirements, payload size implications of base64 photos, or error 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?

Two dense sentences, front-loaded with the metadata change and followed by the picture operations, ending on the important partial-update constraint. The long parenthetical field list is heavy but every item corresponds to a real parameter, so little is wasted.

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 14-parameter mutation tool with no output schema and thin annotations, the description covers the field set, the reference-picture operations, the angle cap, and clearing behavior. It stops short of stating the required identifiers or what the response returns, but an agent has enough to invoke it correctly.

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 only 36%, so the description carries most of the burden, and it does: it maps colloquial names to nearly every parameter (look group → groupLabel, when to use it → useWhen, feature checklist → distinctiveFeatures, framing hint → framingHint) and explains set/clear/add/remove actions for the photo fields. Only the required site/photoId parameters and the exact clearing conventions already stated in the schema are not re-explained.

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 states a specific verb (changes) and resource (a photo bank entry's metadata and reference pictures) and enumerates exactly which fields can be touched, so an agent knows this is a partial edit of an existing photo. It does not explicitly distinguish itself from near siblings such as delete_photo, duplicate_photo, or restore_photo_original, but the scope is clear enough to infer.

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?

There is no statement of when to use this tool versus alternatives (e.g., update_photo vs. get_photo_candidates or upload_post_image), nor any prerequisites such as the photo needing to already exist. The only usage-adjacent cue is the partial-update note ('Only the fields given are changed'), which describes mechanics rather than tool selection.

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