Create Sticker Upload URL

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

Despite annotations indicating a write operation (readOnlyHint=false), the description goes far beyond them with actionable behavior: URL expires in 10 minutes, upload via HTTP PUT with specific content types, sticker saved as soon as PUT succeeds, and step-by-step upload workflow. This provides exceptional transparency for the agent.

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 moderately long but every sentence carries essential information for correct usage. It front-loads the primary action, then follows a logical sequence (how to upload, what not to do, how to fill parameters, expiration). Nothing feels redundant or wasted.

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 tool with no output schema, the description covers all necessary context: the one-time URL, the required HTTP PUT call, content types, the fact that no further tool calls are needed, and the 10-minute expiry. The description is self-sufficient for an agent to invoke and complete the workflow 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?

Schema coverage is 100% with clear parameter descriptions, so baseline is 3. The description adds extra semantic guidance by explaining how to populate the name and emotions parameters: 'If the user already told you what the image is, skip visual analysis and use that description for the name and tags.' This goes beyond schema descriptions.

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 purpose: 'Create a one-time upload URL on this sticker library for the user's attached image bytes/file.' It uses a specific verb and resource, and distinguishes from siblings by specifying 'Use this when adding a sticker from an attachment' and explicitly warning 'do not call add_sticker afterwards.'

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: 'Use this when adding a sticker from an attachment.' It also gives alternatives (do not upload to third-party hosts, do not curl the MCP endpoint) and exclusions (do not call add_sticker afterwards), making the decision boundary clear.

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