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

With no annotations, the description carries the full load and mostly succeeds: it discloses the rate limit (120 req/min vs anonymous), a 100-call daily quota, the metered endpoint families, and the side effect of creating an account bound to the owner's email. It does not say whether the key is returned in the response or emailed to the user, nor what error surfaces for an existing account, which keeps it below 5.

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?

Front-loads the action and the core constraint ('NEW email only') before the quota and upgrade details, so an agent can stop reading early if the case doesn't apply. The mid-section enumerating metered endpoints is dense but does convey what the key unlocks.

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 one-parameter tool with no annotations and no output schema, it covers side effects, quotas, key usage, and the upgrade path. The remaining gap is the response shape and failure behavior (what the caller sees when the email already exists), which the agent would have to discover at runtime.

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 must supply meaning for the single parameter. It does: the email is the agent's owner's, must be requested from the user, and must not be fabricated — guidance not inferable from the bare 'email: string' schema. Format/validation rules are still absent.

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 ('Get a free LiquidVision API key') plus the delivery mechanism ('by email, without a browser'). No sibling tool touches API keys, and the description makes that distinction obvious without needing to compare schemas.

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?

Explicitly scopes the tool to a NEW email and states the exclusion ('an existing account's key is never returned'), routing that case to liquidvision.app/data. It also instructs the agent to ask the user for the email first. It stops short of a direct 'use this when the user has no key yet' directive, but the context is unambiguous.

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