Get Media Upload URLs

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

Annotations only provide readOnlyHint=false and destructiveHint=false, so the description carries the full burden of behavioral disclosure. It clearly reveals that the tool 'only mints a URL' and does not actually upload the file, and it warns about the rejection error if the subsequent PUT is not completed. This is critical behavioral context beyond the structured annotations.

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 dense but efficient: each sentence carries essential information. It front-loads the purpose, then immediately clarifies return values, the critical usage sequence, the preferred alternative, and required parameters. No fluff or redundancy; every sentence earns its place.

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?

Given the tool's moderate complexity and the presence of an output schema, the description covers all essential operational context: what is returned, how to use the returned URLs, the failure mode, a preferred alternative, and the required input fields. Nothing an agent needs to invoke this correctly 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?

The input schema already provides 100% coverage, with descriptions for files, fileName, and mimeType, plus an enum for mimeType. The description repeats 'provide fileName and mimeType' and lists supported types, but adds little new semantic meaning beyond reinforcing the schema. Baseline 3 is appropriate because the schema handles the heavy lifting.

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's function: 'Get presigned upload URLs for direct file uploads.' The verb-resource pairing is specific and distinct. It differentiates itself from sibling tools by naming upload_media as the alternative that performs the upload, and by explaining its role in the create_post workflow.

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?

The description provides explicit when-to-use guidance: 'Prefer the upload_media tool, which performs the upload for you.' It also details the required sequence (PUT to uploadUrl, confirm 2xx before using publicUrl) and states the consequence of non-compliance (create_post/bulk rejects). This leaves no ambiguity about when and how to use the tool.

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