Upload a small file inline

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

Beyond annotations, the description reveals critical behaviors: base64 encoding overhead (~1.35x size), auto-deletion 30 days after publication, and the 'draft' capability limitation. This adds context not available in the readOnlyHint/destructiveHint flags, helping the agent understand side effects and token safety.

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?

Every sentence carries essential information: purpose, size limit, alternative, platform requirements, deletion policy, and capability. The structure is logical and front-loaded with the core purpose, with no 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?

For a 3-parameter tool with no output schema, the description covers all aspects needed for selection and invocation: what it does, when to use it, behavioral caveats, and capability scope. It even describes the return type (hosted public URL) despite no output schema.

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 baseline is 3. The description adds practical meaning to dataBase64 by explaining the base64 encoding overhead and size constraints, which guides the agent in populating parameters correctly. It does not deeply explain each parameter but complements the schema effectively.

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 a specific verb+resource: 'Upload a SMALL image/video inline and get a hosted public URL for schedule_post mediaUrls.' It distinguishes itself from sibling tools by explicitly targeting small files and naming prepare_media_upload + finalize_media_upload as the alternative for larger files.

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?

Provides explicit when-to-use versus alternatives: 'Only practical for tiny files... For ANY real photo or video (over ~100KB) use prepare_media_upload + finalize_media_upload instead.' Also adds platform context (Instagram/TikTok require hosted media) and capability context (draft-only).

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