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

Annotations already disclose readOnlyHint=false, destructiveHint=true, openWorldHint=true and idempotentHint=true. The description adds real behavioral context by revealing that take_over actually rings a live person's phone, which is meaningful given the destructive/open-world flags, but it says nothing about irreversibility, what happens to an in-progress call, or whether repeated joins are safe—despite idempotentHint=true being non-obvious.

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, purpose front-loaded and mode semantics appended, with no redundant or filler wording. Every clause carries information an agent needs to act.

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?

With only two required parameters, full schema coverage, and an output schema covering return values, the description is close to sufficient. The remaining gap is preconditions and side-effect risk, which matter more than usual for a destructive, open-world action.

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 100% and the mode enum already documents both values identically to the description. The description adds no new meaning about call_id format or mode selection beyond what the schema states, so the baseline of 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?

The description uses a specific verb plus resource ("Join a live errand call") and immediately names the two operational modes, which lets an agent distinguish it from read-oriented siblings like check_call_status. It does not explicitly contrast itself with the nearby join_meeting or answer_call_question tools, so the differentiation is implied rather than stated.

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?

"take_over connects the person's own phone; listen returns a signed-in dashboard link" gives concrete guidance for choosing between the two modes, which is the main usage decision for this tool. It stops short of stating prerequisites (e.g., which call states permit joining) or when to prefer a sibling tool instead.

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