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

Annotations mark this as non-read-only but non-destructive, so the agent knows it changes state; the description adds the useful 15-minute validity window and the active-session precondition. It does not disclose whether the prior credential is invalidated, what happens if the session is expired, or any auth/permission requirement — meaningful gaps for a stateful mutation. No contradiction with annotations.

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?

One compact sentence with zero filler; the credential type, TTL, and precondition are all packed into the front-loaded clause.

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 one-parameter tool with a well-documented schema and no output schema requirement, the description covers purpose, TTL, and precondition. A small gap remains: the shape of the returned credential (field names) is unspecified, though the description conveys its nature and lifetime.

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% for the single session_id parameter, and the schema already explains it comes from start_session. The description's only added nuance is that the session must be 'active', which is marginally useful; the schema does the heavy lifting, so baseline 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+resource: retrieves a 'fresh 15-minute proxy credential' tied to an 'active session', which clearly separates it from get_session/start_session/stop_session. It does not explicitly contrast itself with a sibling, so it stops short of 5.

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 phrase 'for an active session' implies the prerequisite that a session must already exist (via start_session), giving implied usage context. However, it never says when to refresh (e.g., before the 15 minutes elapse) or why to use this instead of re-calling start_session, leaving the agent to infer.

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