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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is known. The description adds essential behavioral context: URLs are private and short-lived, signature invalidation on modification, and the need to re-fetch on expiry. This is exactly the kind of nuance that goes beyond structured annotations and prevents misuse.

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 well-structured and front-loaded with the primary purpose, then expands into crucial URL-handling rules. It is slightly verbose but every sentence adds necessary information for correct usage. No fluff; however, it could be tightened slightly without losing value, hence a 4.

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 an output schema present and a single required parameter, the description covers the key behavioral aspects (URL sharing, expiration, signature preservation) that an agent needs to correctly invoke the tool and handle results. Nothing essential 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?

Schema description coverage is 100%, and the schema already documents artifact_id as a string with an example. The description only mentions 'by artifact_id' without adding new meaning about the parameter's format, constraints, or relationship to other data. Baseline 3 is appropriate because the schema does 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?

States a specific verb ('Fetch') and resource ('artifact metadata and a private short-lived download URL') keyed by artifact_id. Clearly distinguishes from siblings like get_artifact_upload_requirements, which serve a different purpose. An agent immediately knows what this tool returns.

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?

Provides rich context on how to handle the returned URL: share verbatim in a code block, not as a clickable link, ask the user to copy it, avoid rewriting or adding tracking params, and call again if expired. This is clear usage guidance, though it does not explicitly name alternative tools or state when not to use it. The guidance is more operational than comparative, so it earns a 4 rather than a 5.

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