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

Annotations already declare readOnlyHint=false and openWorldHint=true, so the lower bar applies. The description does add genuine behavioral signal: the call has two modes, either consuming a supplied API key/token or emitting a sign-in link for out-of-band completion. It stops short of saying whether credentials are persisted, whether a returned link expires, or what happens on failure.

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 sentences, no filler, with the purpose stated before the accepted-input detail. Structure is front-loaded and appropriate for the amount of information given, though the second sentence compresses three distinct inputs into one clause at the cost of clarity.

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 five-parameter authorization tool with zero schema descriptions and no required parameters, the description leaves too many decisions open: which identifier selects the service, whether a credential and a service must be paired, and how to proceed when a sign-in link is returned. The presence of an output schema excuses it from explaining return values, but not from the input-selection ambiguity.

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% across five nullable parameters, so the description carries the full burden and largely fails it. 'Accepts an API key or token' loosely gestures at api_key/auth_token/bearer_token but never distinguishes them, never explains whether they are mutually exclusive, and leaves service and adapter_id entirely unexplained — arguably the most important parameter for choosing what to authorize.

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 names a concrete outcome — connecting your own account/API key for a service — and adds the distinguishing detail that it either accepts credentials or returns a sign-in link. That is enough to separate it from siblings like account, confirm, or invoke. It loses a point only because the verb is soft ('Connect') and the scope of 'service' is never grounded.

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 supplies a real trigger condition ('to continue past the free trial'), which tells the agent when this tool becomes relevant. However, it names no alternative path (e.g., when to use account instead, or what to do if the sign-in link flow is preferred) and offers no when-not guidance. Usage is implied rather than specified.

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