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

With no annotations provided, the description carries the full behavioral burden, and it delivers: one-time key revelation ('shown in this answer and never again'), the required auth header format, side effects on hold/cancel budget ownership, and the 3-per-day rate limit. This is rich disclosure of persistence, security, and side-effect behavior.

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 dense but every clause earns its place: purpose, outputs, key handling, sibling routing, budget semantics, and rate limit. Core purpose is front-loaded in the first sentence and later sentences build context in a logical order. Slightly long, but justified given zero annotations and no output schema.

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, the description covers what an agent needs: what is returned (id + key), how to use the returned key, which operations require it, side effects, and rate limits. Minor tension between 'once' and '3 registrations per day' is resolved by the closing sentence, leaving little missing.

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% and the schema's own description already fully explains `name`, including that it is not a secret and not a login. The tool description adds no parameter-level semantics, but none is needed — the schema has done the work, so the baseline 3 applies.

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 states a specific operation — registering an agent to obtain its own identity — and names concrete outputs (`agent` id and `key`). It differentiates from booking-related siblings by naming which operations require the key (hold_slot, confirm_booking, cancel_booking) and which do not (find_offers, reading a session).

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 gives explicit routing guidance: which sibling tools need the key and which do not, plus the operational rule 'register once and keep the key, do not mint one per conversation.' It also discloses the per-client daily limit of 3 registrations, so an agent knows exactly when and how often to call this tool.

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