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

Beyond the annotations (which only say it is a non-destructive, non-open-world write), the description discloses a 16 MiB payload cap, content-addressed dedupe ('identical bytes return the same managed id'), the asin side effect that populates parent/sku/brand, BETA status and per-tier export quotas. That is substantive behavioral context an agent cannot get from the structured fields.

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 action list and keeps the whole definition to a short paragraph with no filler sentences. The BETA/quota sentence is dense and slightly tangential to invocation mechanics, but it is useful for interpreting outcomes.

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 13-parameter, three-action mutation tool with no output schema, the description covers action selection, payload limits, dedupe return behavior and where to find the exact per-action schema. It does not describe result shapes for tag or save_render, though pointing at video_guide mitigates that.

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 only 23% across 13 params, so the description has to carry the load, and it does: filename/dataBase64 size limit, assetId and jobId roles, tag add/remove/set semantics, and the shared tags/brand/asin/sku/type fields. It stops short of documenting every parameter's accepted values (those live in the schema), so not quite a 5.

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 family (library writes) plus the resource, then enumerates the three concrete actions with their key inputs. It explicitly distinguishes itself from the sibling video_upload_slot for real files, so an agent can route without opening either 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?

It gives explicit routing rules: prefer video_upload_slot for real files, and call video_guide first for the catalog, per-action schema and account tier notes. Per-action conditions (upload vs tag vs save_render) are spelled out rather than left to inference.

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