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

Annotations only cover the safety triad (non-read-only, non-destructive, closed-world), while the description adds genuinely useful behavior: accepted formats, a 10 MB ceiling, a rate limit of 40 per day while testing, and an authentication requirement. One mild tension exists between "public web address" and openWorldHint=false, but the tool still operates on internal booking-page state, so this is not a true contradiction.

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 sentences, zero filler: target and constraints first, then operational limits and the auth requirement. Every clause carries distinct information an agent needs before calling.

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 mutation tool with no output schema, the description covers inputs, size/format limits, quota, auth, and targeting scope. It stops short of explaining what happens to an existing cover photo when cover=true or how to remove a photo, which would round out the mutation semantics.

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 all four parameters are already documented, and the description only echoes the room_type semantics ("the hotel, or one room type"). It adds the source constraints around url but nothing new about cover or caption, so the baseline 3 is appropriate.

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 ("Adds a picture ... to the booking page") and disambiguates the two possible targets: the hotel, or one room type. The accepted formats, size cap, and source type are all named, so an agent can tell this apart from siblings like set_logo or upload_report without opening the 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?

The description gives a prerequisite ("Needs the owner's sign-in") and implies usage through the hotel-vs-room-type target split, but never says when to use this instead of set_logo, upload_report, or other media-related siblings. No explicit exclusions or alternative-routing guidance is provided.

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