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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description layers on semantics the annotations cannot: confidence tiers (confirmed vs seen, two independent domains vs one), the no-observation case returning 'status unknown' with no fields and 'never a guess', and the side effect that a market miss is queued as a lead. This is unusually rich behavioral disclosure.

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 critical information (what it returns, confidence, negative case) is front-loaded in the first sentences. It is dense and stylized ('this door's', 'the hub's gate'), which costs a little readability, but nearly every clause carries payload.

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?

Despite an output schema existing, the description usefully frames return shape and, more importantly, disambiguates confidence and empty-result semantics that a bare schema would not. Nothing an agent needs to call or interpret this tool is 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%, so the baseline is 3, but the description adds real meaning beyond the schema: 'market' is a hub market code with the UK-for-GB alias, and passing it changes behavior by queuing a miss as a lead for that market. That is substance the schema's 'e.g. UK, US, FR' does not convey.

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?

Specific verb+resource ('Returns the signed record for a GTIN-8/12/13/14') with the exact scope of returned identity fields spelled out. An agent knows precisely what lookup this performs and what an empty result means, without opening the 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?

It gives clear context for when to call (resolve a GTIN's identity, optionally tagging a market) and explicitly excludes a neighboring concern: 'Can it be sold there is the hub's gate, not this door's.' No siblings exist, so there is no alternative to route between, but the exclusion is valuable.

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