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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true; the description adds genuinely new context that ending 'stops billing immediately,' which explains the cost consequence of the mutation. It stops short of saying the action is irreversible or what happens on a repeat call (relevant given idempotentHint=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?

Three short sentences, front-loaded with the action and its trigger, with no filler. Every sentence carries actionable information.

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 single-parameter terminal tool with no output schema, the description covers what it does, when to call it, and the billing effect. The only meaningful gap is the non-idempotent behavior — whether a second call errors or how to confirm the session actually ended.

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 parameter, so the schema already documents session_id and the baseline is 3. The description adds no format, source, or validity information about the identifier beyond what the schema states.

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 ('End the session') plus the condition that triggers it ('when the task is done'). The sibling tools are all read/send/expert operations, so this terminal action is unambiguously distinguishable.

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 an explicit usage rule: 'Always call this when you are finished,' which tells the agent when to invoke it. It does not discuss failure modes or what to do if the session is already closed, but for a terminal one-shot action the guidance is clear.

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