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

Annotations already declare destructiveHint=true, openWorldHint=true and readOnlyHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the goodbye string is spoken first in a keep_open conversation, and an empty value hangs up silently.

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, front-loaded with the core action and immediately followed by the only non-obvious parameter behavior, with a concrete example. No padding, though 'leave it empty to just hang up' is slightly awkward phrasing.

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 and the description covers the key goodbye semantics, but for a destructive, open-world tool it omits what happens on error, whether the call must be active, and any auth requirements for `session_token`. Adequate but with clear gaps.

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 description coverage is 0%, so the description carries the burden. It explains the optional `goodbye` parameter and its default-empty behavior well, but says nothing about `call_id` or `session_token` beyond their self-evident names, leaving two required parameters effectively undocumented.

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 call you placed'), which distinguishes it from the sibling `call` (which places calls) and `say` (which speaks without ending). However, it never names those siblings or explicitly contrasts scope, so an agent must infer the boundary.

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?

Usage is implied by 'a call you placed' and the goodbye guidance tells the agent how to use the tool in a keep_open conversation, but there is no explicit when-to-use vs. alternatives statement (e.g., versus `say` or `wait_for_reply`) and no prerequisites spelled out.

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