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

The annotations already declare readOnlyHint=true and idempotentHint=true, so the read-only behavior is known. The description adds valuable behavioral context by detailing the three possible statuses (pending, uploaded, expired) and the 15-minute session expiry limit. This goes beyond what annotations provide and helps the agent understand polling behavior and expected return states.

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 compact and well-structured. It opens with a one-sentence purpose, follows with a single usage instruction, and then uses a concise bullet list for return states. Every sentence adds value, and there is no redundancy or fluff.

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 simple one-parameter polling tool with an output schema (which likely details the return structure), the description provides sufficient context: it explains the main status states, the expiry limit, and when to call it. The combination of the description, annotations, and schema fully equips the agent to use the tool 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 input schema has 100% description coverage: the single parameter 'sessionId' is described as 'The session ID returned from create_upload_session.' The description does not add any semantic meaning beyond the schema, so the baseline score of 3 is appropriate because the schema carries the full burden.

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 uses a specific verb and resource: 'Check the status of an upload session and get the media URL(s) once uploaded.' This clearly defines the tool's function and distinguishes it from sibling tools like create_upload_session, which creates the session, and check_ai_media_status, which likely handles AI media statuses. The purpose is unambiguous and specific.

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 timing guidance: 'Call this after the user clicks the upload link to see if they've completed the upload.' This clearly indicates when to use the tool and implies the preceding creation step. However, it does not explicitly name alternatives or explain when not to use it, so it falls just short of a perfect score.

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