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

With no annotations, the description carries the behavioral disclosure burden and does it well: it says the tool waits for load completion, returns the final URL after redirects, and automatically percent-encodes characters Safari would otherwise reject. It does not describe timeout or failure behavior, but adds substantial useful behavioral context.

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, front-loaded with the core action, and uses a clear Args block. Every sentence adds value: behavior, return value, encoding quirk, and parameter semantics are all covered without redundancy.

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 two-parameter navigation tool, the description is complete: it defines tab addressing, URL handling, load-waiting behavior, and redirect awareness. The output schema exists, and the description already provides the important return meaning. No critical calling context 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 description coverage is 0%, so the description must explain the parameters. It does: 'tab' gets rich semantics (index within window 1, or substring of URL/title), and 'url' receives context from the percent-encoding note. 'Where to send it' is minimal, but the overall description compensates well.

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 verb and resource: 'Point an existing tab at a URL and wait for the load to complete.' It clearly distinguishes itself from siblings like open_tab by emphasizing 'existing tab,' and from read_page by focusing on navigation.

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 when to use the tool (when you need an existing tab to navigate to a URL), but it never explicitly names alternatives or states when not to use it. The 'existing tab' wording hints at the distinction from open_tab, but the guidance is left to inference.

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