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

Beyond the annotations (which already declare this is a non-read-only but non-destructive, closed-world write), the description adds real behavioral facts: an unknown id is a silent no-op, a tab's kind is immutable, and the write scope is required. That is meaningful context an agent cannot get from readOnlyHint/destructiveHint alone.

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 action is not front-loaded: three sentences describe what a panel is, who shares it, and rollout status before the tool's actual behavior appears. Much of that preamble is product context rather than invocation-relevant guidance, and the useful constraints (immutable kind, no-op on unknown id, write scope) are compressed into the final two clauses.

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?

With an output schema present and full parameter descriptions, the description needn't explain returns. It covers the mutation contract (kind fixed, unknown id no-op, write scope) and orients an agent unfamiliar with the panel concept, leaving only minor gaps around focus behavior and how patch fields are replaced.

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%, so the schema already documents all four parameters including the conversation_id default and the focus flag. The description adds only illustrative patch content ('a new title, more search hits, the calendar's highlight'), which largely duplicates the schema's own patch example. Baseline 3 applies.

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 operative sentence — 'Changes fields of an open tab (a new title, more search hits, the calendar's highlight); its kind never changes' — names a specific verb, resource, and mutation boundary. This implicitly separates it from panel_open (creates) and panel_close (removes). However, that sentence is buried behind three sentences of world-building, so an agent scanning the first line gets context rather than the action.

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?

Usage is only implied: 'an open tab' and 'An id not on the panel changes nothing' suggest panel_open must run first, but no sibling is named and no explicit when-not guidance is given. An agent must infer the open-before-update ordering and the choice against panel_open/panel_watch.

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