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

Annotations only supply the safety profile (readOnlyHint/openWorldHint/destructiveHint); the description adds the actionable behavioral context: file-type and size/count limits, the interactive handoff where the user uploads and then supplies media IDs, the requirement to pass IDs to create_post in carousel order, and the instruction not to use other upload tools for those files.

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 purpose and constraints in the first sentence, then routes alternatives. Slightly dense with repeated emphasis on not using other upload tools, but every sentence carries decision-relevant information.

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 and only minimal annotations, the description carries the full burden and does so: it explains the interaction flow, limits, exclusions, and the follow-up create_post call. An agent has everything needed to invoke and follow through correctly.

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?

The tool takes zero parameters, so the baseline is 4. The description nonetheless documents the implicit inputs the agent must handle in the follow-up turn (media IDs in order), which is more than a bare no-parameter tool would provide.

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 action (show an upload box in chat) with scope details (images/videos/PDFs, 300MB, 20 files) and explicitly distinguishes itself from sibling tools like upload_attached_file and the other upload tools. An agent can route correctly without opening other schemas.

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-to-use (files from user's device, not at a public URL, not yet in chat, or too large to attach) and when-not-to-use (files already attached in chat -> upload_attached_file). It also names the downstream step (create_post) and the required ordering, leaving nothing to inference.

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