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

Beyond annotations (which show no readOnly/idempotent hints), the description discloses critical behaviors: silent truncation when base64 exceeds context cap, 5MB server-side limit, allowed content types, and failure modes with fallback instructions. This adds substantial context that annotations alone do not provide.

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?

The description is lengthy but front-loaded with the most critical warning about size limits, followed by usage and fallback. Every section adds necessary context, though it could be tightened. The warning is placed first, which is good for agent attention.

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?

Covers usage, limits, allowed types, failure modes, and fallback. The output schema exists and the description mentions the returned URL, so completeness is high. Given the tool's complexity and the importance of the warning, nothing critical is missing.

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 0%, so the description carries the burden. It mentions the base64 path and size limits, and lists allowed types matching the enum, but does not explicitly describe filename or contentType beyond the purpose. It adds some value but not comprehensive parameter guidance for all three parameters.

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 clearly states the tool uploads an image or video via base64 to the asset library and returns a URL for use in create_post_draft.mediaUrls. It also distinguishes it from sibling request_asset_upload by explicitly naming the alternative, making the purpose unambiguous.

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?

Explicitly states when to use this tool vs. the sibling: 'For anything larger, USE request_asset_upload instead' and explains the cap. It also provides a detailed fallback (manual upload) for sandboxed environments, covering both alternative paths and exclusions.

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