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

With no annotations, the description carries the full burden, and it does disclose the key traits: this mutates state (creates account and voice agent), returns the API key, agent id and embed snippet, and the same payload can be polled later. It leaves out failure behavior, whether the intent_token or spt is single-use, and whether retries are idempotent or duplicate the account.

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 dense sentences, front-loaded with the action and the token constraint, with the mutation/return profile and the polling path following logically. The parenthetical on test-token character rules partially duplicates the schema's regex pattern, which is minor waste.

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 two-parameter mutation tool with no annotations and no output schema, the description does reasonable work by enumerating return values and the test-mode gate. The critical gap is where 'intent_token' comes from and whether it is consumed by a call, which an agent needs to invoke this 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 0%, so the description must compensate. It adds real meaning for 'spt' (Stripe Shared Payment Token, plus the test-token form allowed under AGENTIC_ALLOW_TEST_CHECKOUT=1), but 'intent_token' is never explained at all — no provenance, no hint that it is the asgi_ value issued earlier in the flow — so one of two required parameters remains opaque.

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 ('Complete an agentic signup') and immediately scopes it to the two token types accepted. It also names the sibling it relates to ('The same payload can be polled later via vf_get_signup_status'), so an agent can separate it from vf_signup and vf_get_signup_status without opening either 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?

Gives a concrete conditional for the test path ('when AGENTIC_ALLOW_TEST_CHECKOUT=1') and points at vf_get_signup_status as the alternative for retrieving the result later. It never explicitly contrasts itself with the sibling vf_signup, so the agent must infer which signup flow applies.

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