create_multi_channel_verification

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

Beyond the readOnlyHint=false/destructiveHint=false annotations, it discloses billing semantics (exactly one proof billed at the winning channel's completion, nothing at creation), that losing sibling channels are cancelled, and that most clients hide tool results so the agent must surface actionable content in its own reply. These are the kinds of side effects and UX constraints annotations cannot convey.

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?

It is a long description, but it is front-loaded with purpose before agent instructions, then caveats, then access requirements, and each paragraph carries operative content (billing, link handling, QR verbatim rule, polling target). No sentence is purely decorative, though the length is near the upper bound for a single tool.

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 no output schema, the description compensates by documenting the response shape (group_id, channels array, deep_link, sms_message, qr_text) and the follow-up polling tool. Combined with the coverage of prerequisites, billing, and user-visible rendering rules, an agent has everything needed to invoke and complete the flow correctly.

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%, so the baseline is 3, but the description adds genuine meaning: the channels list is attempted in parallel with first-wins cancellation, and responses carry group_id (vg_<hex>), a channels array with deep_link/sms_message, and qr_text as pre-rendered art rather than an alternate address. That clarifies semantics the schema alone does not.

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 opening sentence names a specific verb+resource (create a multi-channel phone verification) and immediately defines the distinctive mechanism: one phone number challenged over several channels at once with OR/first-wins semantics. That mechanism cleanly separates it from siblings such as create_verification, create_verification_request, and start_2fa without ambiguity.

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?

It gives an explicit workflow: pass the returned deep_link to render_auth_link, poll get_multi_channel_verification_status with the group_id, and present the SMS text/number to the user. It also states a when-not (start_login does NOT open this tool) and a precondition (needs a Proof account with PROOF_API_KEY set).

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