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

Annotations already declare destructiveHint=true and idempotentHint=true; the description goes further by explaining that the hangup is immediate and affects both parties, and that an already-ended call is a no-op returning hung_up false. It also notes the downstream aftermath (summary, transcript, recording still arrive), which is genuinely useful context an agent would not get from 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?

Three short sentences, front-loaded with the core action, then scope, then edge-case behaviour. No filler or restatement of the tool name.

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?

An output schema exists, so return values need not be described; the description nonetheless adds the hung_up false no-op case and the post-call artifact flow. For a single-parameter tool this is fully sufficient.

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 only one parameter and schema description coverage is 100%, so the schema already documents call_ref and its provenance. The description's mention of wa_ai_call_start/wa_ai_list_calls duplicates the schema text rather than adding new meaning, 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 ('End') and resource ('a live AI voice-agent call'), and explicitly scopes it to calls started via wa_ai_call_start or answered incoming calls. This clearly separates it from wa_ai_call_start, wa_ai_call_get and wa_ai_list_calls without requiring the schema.

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?

Names the two situations where it applies (a call you started, or an incoming call an agent answered) and covers the edge case of an already-ended call. It does not name an explicit alternative or exclusion, but the context is clear enough to select it confidently.

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