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

Annotations already indicate readOnlyHint=false and the description adds that this unlocks purchase tools. The description frames the tool as free and unconditional, and mentions it accesses hfspaces. Missing disclosure: exactly what state changes occur on the session, whether this is idempotent, whether calling multiple times has side effects. Description does not contradict annotations.

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?

The description is compact and front-loaded with the actionable signal (no API key needed, call now). Three short clauses convey value. Slight promotional tone but no wasted sentences. It earns its length.

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?

Given the schema and output schema carry the parameters, and no required params exist, the description sufficiently covers the minimal call. It names the unlock purpose and the cost. Could mention that {} is valid registration, and lacks explicit behavioral side effects, but with zero required params and a rich schema, it is reasonably complete for the action of calling register.

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 schema documents all 15 parameters thoroughly. The description adds no parameter-specific guidance; it simply points at registration without mapping any parameters. Baseline 3 is appropriate since the schema does the heavy lifting, and the description doesn't need to compensate.

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 clearly states this tool registers the session to unlock purchase tools, with a specific offer (free, no API key needed). It distinguishes from siblings like onboard_start implicitly, though it doesn't explicitly differentiate from other registration-related tools. The verb 'call register' is explicit and the target session is clear.

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?

The description explicitly says to call this now, and declares no prerequisites (no API key, no wallet). However, it doesn't mention alternatives or when not to use it, nor does it elaborate on the actual registration flow with parameters. The urgency and lack-of-prerequisite framing provides decent usage guidance for a free onboarding tool.

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