Legacy: brief → url.open

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds the routing behavior (type-dependent endpoint selection) and mentions HTTP 402 unpaid, which is a behavioral trait not in annotations. However, 'Score lower is better' is ambiguous and unexplained, and the description doesn't clarify what 'stack or Bearer 54k_.' means. It adds some context but is cryptic.

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 short and front-loaded with the legacy alias and preference for url.open. However, the trailing 'Score lower is better. HTTP 402 unpaid — stack or Bearer 54k_.' is cryptic and unexplained, which wastes the agent's time trying to interpret it. It's not concise in the sense of every sentence earning its place; the last part is confusing and likely noise.

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 legacy alias with annotations covering safety and idempotency, the description provides routing logic and a preference for the alternative. However, the cryptic 'Score lower is better' and 'HTTP 402 unpaid — stack or Bearer 54k_.' are unexplained and could mislead an agent. There's no output schema, so the description could have clarified return values or error handling, but it doesn't. It's adequate but with clear gaps.

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 100%, so the schema already documents both parameters (q and type) with descriptions. The description adds the routing semantics: type=url maps to /v1/open, address|token maps to /v1/brief. This is useful but partially redundant with the schema's type description ('Prefer 'url' → /v1/open'). The description doesn't add much beyond what the schema already says, so baseline 3 is appropriate.

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 identifies this as a legacy alias for url.open, with a specific verb ('brief'/'open') and resource (URL/address/token). It distinguishes itself from url.open by labeling itself as legacy and directing preference to url.open. However, the description is somewhat cryptic with 'Score lower is better' and 'HTTP 402 unpaid — stack or Bearer 54k_.' which may confuse an agent about the actual purpose.

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 'Prefer url.open' and provides routing logic: 'type=url → GET /v1/open; address|token → GET /v1/brief.' This gives clear when-to-use guidance and names the alternative. It doesn't explicitly state when NOT to use this tool, but the legacy alias designation and preference for url.open serve as a clear exclusion. The cryptic 'Score lower is better' and 'HTTP 402 unpaid' add some noise but don't undermine the routing guidance.

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