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

The annotations already indicate this is not read-only. The description adds meaningful behavioral constraints: the ~90 KiB MCP limit, the Pro account requirement, and the fact that the tool returns an attachment id for later use. This goes beyond what annotations provide, though it does not discuss retention or cleanup.

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?

Two sentences, front-loaded with the key constraint and purpose. The final sentence routes to alternatives without padding. Every clause 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?

With a fully described input schema and an output schema present, the description covers the essential selection and invocation context: size limit, account requirement, resulting id, and alternative for larger files. Nothing needed to call the tool 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 has 100% parameter descriptions, so the schema already documents filename, mime_type, and content_base64. The description adds minimal parameter-level meaning beyond 'upload a file'; it mostly restates the body content. Baseline 3 is appropriate because the schema carries the load.

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 names a specific verb and resource: 'Upload a small file' and states the outcome: 'get an attachment id to include in broadcast or ask_question via attachment_ids.' This clearly distinguishes the tool from siblings like get_attachment and delete_attachment.

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 explicitly says when to use this tool (small files, for use with broadcast/ask_question) and when not to use it: 'Larger files: use the PingRoom CLI or agent REST API.' This is concrete routing guidance, not vague context.

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