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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered. The description adds genuinely non-obvious context beyond them: ending a collaboration does not affect the underlying friendship relationship. It stops short of saying whether the other participant is notified or whether the action can be undone.

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?

Two short sentences with the scope stated first and the side-effect note second; nothing is redundant. The phrase 'Friendship remains separate' is slightly clipped and could be read as vague, which keeps it from a 5.

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-identifier destructive mutation with rich annotations, the definition covers scope and one important side effect. Missing is the post-call behavior an agent might want to promise the user: notification of the other party, resulting state of the session, or failure modes if the session is already 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?

Only one parameter with 100% schema description coverage, so the schema already explains the session identifier fully. The description adds marginal framing ('a session you participate in') but no format, sourcing, or constraint detail beyond the schema, so the 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 and resource ('End a ... session') and scopes it precisely to pending or active sessions the caller participates in, regardless of initiator. It is clearly distinct from view_end_collaboration and decline_collaboration without needing to name them, though it never explicitly contrasts them.

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?

'Pending or active' and 'regardless of who initiated it' give real boundary conditions for when this applies, which is more than nothing. However, it does not say when to prefer decline_collaboration or cancel-style siblings over ending, so the agent must infer the distinction between declining an invitation and terminating an existing session.

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