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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds context annotations cannot carry, namely that the call is free and that its result previews what exit_ise_session will terminate. It does not discuss return format, which is what keeps it from a 5.

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?

Three short sentences, zero filler, with the purpose front-loaded before the cost and the cross-tool hint. Every sentence 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?

No output schema exists, yet the description names the three things the agent gets back (session existence, elapsed time, billing mode), which is sufficient for a trivial read-only status check with one optional auth parameter.

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?

There is a single, fully documented auth_token with 100% schema description coverage, so the schema already carries the parameter semantics. The description adds nothing about the parameter, making the baseline 3 appropriate.

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 ('Check whether you have an active ISE session') plus the exact fields returned ('elapsed time and billing mode'), and explicitly ties itself to the sibling exit_ise_session rather than leaving that relation implicit.

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?

Gives clear context for use ('Use this to find out what exit_ise_session will close') and names the cost ('Free'), so the agent knows the scenario. It stops short of an explicit when-not / alternative routing statement, so a 4 rather than 5.

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