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

Annotations already declare non-read-only, non-idempotent, open-world behavior, so the description's added value is the disclosure that usage is charged to the member's own data and that starting a session ends the member's other active connection. Those are meaningful side effects beyond the annotations. The return contents are also described, though the 'Ends other active connection' side effect sits slightly awkwardly against destructiveHint=false.

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?

Four compact sentences, front-loaded with the operation and recipient, followed by return values, billing, and the side effect. No sentence is 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 three-parameter tool with no output schema, the description covers the operation, return shape, credential lifetime, billing, and session side effect. It is nearly complete, with only explicit sibling routing left implicit.

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%, so max_mb, region, and max_minutes are already documented in the input schema. The description adds no parameter-specific meaning beyond noting a 15-minute credential, so the baseline of 3 applies.

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 and resource ('Start a short-lived HTTPS (TLS) CONNECT proxy session') and identifies the owning member as the subject. The agent can distinguish this from get_session and refresh_credential without opening another schema.

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?

Implies the operational context through 'short-lived' and the side effect of ending the member's other active connection, which signals this creates a replacement session. It does not explicitly say when to use this versus get_session or refresh_credential, leaving the choice to inference.

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