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

Annotations declare the mutation profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the description adds genuinely useful context beyond them: operations chain each on the previous file's output, a run past 4 minutes returns the in-progress job plus remaining operations, and the call is free of credits. Omits details like retry/failure semantics, but the timeout and pipelining disclosures are substantive.

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-loads the core mechanism (up to 6 chained operations) before secondary details like timeout behavior and prerequisites. Dense but nearly every sentence carries required information; the music-rights clause is slightly awkwardly appended.

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 compensates by explaining the return value (the last job, whose result links the finished file) and the partial-run case. Combined with prerequisites and the 4-minute boundary, an agent has enough to invoke it correctly, though failure/error behavior is not covered.

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 per-operation parameters (trim start/end, captions cues/transcript, reformat mode/aspect_ratio, overlay/end_card brand, mix music) are fully documented in the schema. The description adds the meaningful ordering rule (operations run in sequence) but does not extend individual parameter semantics, so 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 ('runs up to 6 finishing operations... on a clip') and enumerates the six operations, so the agent knows exactly what the tool produces. It names sibling tools (ugcfans_list_files, ugcfans_transcribe, upload URL) and distinguishes itself from them.

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 clear prerequisites and routing: the clip must already be in the library, upload at the given URL, resolve its address with ugcfans_list_files, and use ugcfans_transcribe for transcripts. It doesn't state when NOT to use the tool, but the sequencing and dependency guidance is explicit.

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