Get Thumbnail (EVS)

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

Annotations already establish readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable context: the EVS endpoint, the prerequisite of a prior listing call, and the fact that there is no default or guessable timestamp. It does not describe the exact response body, but that is a minor gap for a read-only preview endpoint.

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 deliver the central behavior, endpoint, and the two critical constraints with no filler. The content is front-loaded and every clause adds necessary context.

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?

Together with the richly documented schema and readOnly annotation, the description gives an agent the prerequisites and constraints needed to call the tool correctly. The only missing piece is an explicit description of the response format (e.g., binary image vs URL), which is not present since there is no output schema.

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?

The input schema already documents all three parameters at 100% coverage, including path format examples and timestamp provenance, so the description does not need to carry the burden. It reinforces the lmd_web requirement but does not add meaning beyond the schema. 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?

The description names a specific operation ('Fetches a thumbnail preview image') and a resource ('a backed-up file'), and identifies the exact endpoint. It is clearly distinct from siblings like download_file and list_files because it targets preview images only.

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 explicitly tells the agent that path must be in EVS format and that timestamp must be the lmd_web value from a prior list_files or browse_folder call, adding the warning that a timestamp cannot be guessed. It does not explicitly compare against download_file or other alternatives, so it earns 4 rather than 5.

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