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

Annotations already declare it is a non-idempotent write that is not destructive. The description adds genuinely useful behavior beyond that: the 402 payment-gate response shape with `accepts[]` and the 'pay and repeat' recovery path. It does not cover auth scope beyond guest_token, but the added billing semantics are valuable.

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 short sentences, front-loaded with the core action and followed by the edge-case response. Every clause earns its place with no filler.

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 mutation tool with no output schema and no annotations covering failure modes, the description covers the main operational surprise (the 402 paywall). The remaining gap is the undocumented guest_token parameter, but overall it is sufficient to call the tool correctly.

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 67%; url and alias are documented in the schema, while guest_token is undocumented in both. The description mentions the URL concept but adds no format, alias behavior, or guest_token meaning beyond what the schema already provides.

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?

States a specific verb and resource: 'Opens a tab for a URL in the workspace.' This clearly separates it from read/list siblings like list_tabs, tab_history, and watch_tab. It stops short of naming those siblings or contrasting behavior, but the core purpose is unambiguous.

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 implies usage (create a tab for a URL) and adds a failure condition, the 402 when past the free allowance, but never states when to choose this over run_tab or watch_tab. Usage is inferred rather than guided.

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