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

Annotations declare the safety profile (not read-only, not destructive, not idempotent), and the description adds behavior beyond that: a hard cap of 5 tabs and the popup-never-auto-selected rule. Worth noting: a tool whose op enum includes 'close' sits somewhat awkwardly with destructiveHint=false, though the description itself doesn't contradict the annotation.

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, capabilities front-loaded, the popup caveat second. No filler and nothing that could be cut without losing meaning.

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?

No output schema exists, and the description implies that 'list' yields tab identifiers suitable for 'select', which is adequate for a 4-op multiplexed tool. It does not say what a close returns or whether closing the last tab is an error, leaving a small gap.

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 80%, so op/tab/url/session_id/secret are already documented in structured fields. The description adds only the 'max 5' bound and the list-then-select ordering; it says nothing extra about tab id format, url semantics, or what happens when the 5-tab cap is exceeded.

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?

Opens with a concrete verb set (list, open, switch, close) bound to a specific resource (tabs), and the max-5 constraint scopes the resource. It doesn't explicitly distinguish itself from navigate/act, which an agent might reasonably confuse with 'open' or 'switch', so it falls short of the 5 bar.

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 an actionable sequencing rule: 'Popups open as new tabs but are not selected: list, then select.' That is real when-to-do-what guidance an agent can follow. No exclusions or alternatives among siblings (act vs navigate vs tabs) are stated.

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