tab_select

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

Goes well beyond readOnlyHint=false / openWorldHint=true: it discloses the side effect (fronts the tab and changes the default target of all page tools), the non-effects ('Does not reload or change the page'), the return value (title and URL), and the error behavior for unknown ids. Nothing here contradicts the annotations — readOnlyHint=false is consistent with the client-side state change of switching the active target.

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?

Four short sentences, each carrying distinct information: effect, return value, id source/error, non-effects, and the alternative path. The core effect is front-loaded and the escape hatch ('pass `tab` to that tool instead') closes the definition without padding.

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, non-readonly tool with no output schema, the description covers effect, side effects, return values, id sourcing, error case, and the do-not-switch alternative. An agent can call this correctly without consulting anything else.

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 property description already explains the tab id, so the baseline is 3. The description earns the extra point by adding provenance (tabs_list or tab_new) and the invalid-id outcome, which are not in the schema.

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+resource ('Switch to an existing tab') and immediately defines the mechanism and effect: brings it to the front and makes it the default target of all page tools. This clearly separates it from tab_new, tab_close, and tabs_list by naming the tab-lifecycle siblings in the id-sourcing sentence.

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?

Gives explicit when-to-use routing ('Get ids from tabs_list or tab_new') and an explicit alternative for the case where switching is unnecessary: 'To act on a tab once without switching, pass `tab` to that tool instead.' It also states the failure mode for an unknown id, so the agent knows what a bad call looks like.

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