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

Beyond the annotations (write, non-destructive, non-idempotent), the description discloses the silent-truncation failure mode, the gap between the server-side 5MB cap and the effective client-side cap, allowed MIME types, and plan storage limits. These are non-obvious behavioral traits the annotations cannot convey.

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 decisive 'don't use this by default' warning and uses clear caps-styled emphasis. It is somewhat long and repeats the size-cap idea in three places ('~8KB or less', '~10-15KB chars', 'server cap'), but each block carries actionable content rather than filler.

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?

An output schema exists, so return values need no elaboration, and the description still covers caps, allowed types, plan limits, the preferred alternative, and a network-failure fallback. For a three-param write tool, an agent has everything needed to decide whether and how to call it.

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% and none of the three parameters carries a description, so the description must compensate. It partially does: it states the 5MB cap (relevant to base64), lists allowed types (matching the contentType enum), and implies the filename role. However it never clarifies the base64 format (raw vs. data-URI prefix) or filename constraints, leaving a real gap for a required param.

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: 'uploads an image or video to your PostNext asset library via base64 and returns a URL for create_post_draft.mediaUrls.' It explicitly distinguishes itself from the sibling tool request_asset_upload, so an agent can tell the two apart 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?

Gives explicit when/when-not rules (use only for very small files ~8KB or less; use request_asset_upload for anything larger) and a documented last-resort fallback for environments where neither upload tool can transfer bytes. Alternatives and selection conditions are fully spelled out.

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