get_frame

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds two pieces of behavioral context beyond that: the authentication requirement and the return form (an inline JPEG rather than a URL or metadata). It stops short of noting errors for out-of-range timestamps or download behavior, so it isn't fully transparent.

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 short clauses with no filler, and the output format leads ahead of the auth requirement. The only weakness is that brevity shades into under-specification rather than pure efficiency.

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 simple three-parameter tool with full schema coverage and no output schema, the description covers auth and return format, which is the minimum an agent needs. However, it says nothing about failure modes (invalid link, timestamp beyond video length) or whether the frame is fetched remotely, which would be valuable for an openWorld read.

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 100%, so the schema already documents url, page, and timestamp thoroughly, including defaults and edge cases. The description adds no parameter detail whatsoever, 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?

The description states the output ('returns an inline JPEG image') and the keyword tags '(video frame, screenshot)' combined with the name get_frame make the function clear: fetch a still frame from a video. It doesn't explicitly say it extracts the frame at a given timestamp, but the schema fills that in, and no sibling competes for the same purpose.

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?

'Login required' is a useful precondition for invoking the tool, but there is no guidance on when to choose this over siblings like get_video_info or get_subtitles. Usage is only implied by the tool's name and the required timestamp parameter.

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