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

Adds substantial behavior beyond the thin annotations: the resulting ordering position relative to previously pinned apps, persistence across update_app, the not_installed error, and that the action is written to device_log. These are exactly the traits an agent needs (reversibility, durability, failure mode, auditability) and they are consistent with readOnlyHint=false and destructiveHint=false.

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 dense sentences with the primary action front-loaded and supporting facts (app-type scope, persistence, error, logging) trailing in priority order. No filler or repetition; every clause carries distinct information.

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 simple 3-parameter mutation with no output schema, the description covers action, toggle, eligibility scope, persistence, failure mode, and audit logging — nearly everything an agent needs. The one gap is the absence of any explicit sibling comparison (e.g. how this differs from hide_app), which keeps it just short of fully complete.

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 all three parameters are already documented, including pinned's boolean meaning. The description's 'unpin it with pinned: false' largely restates the schema; it adds the app-type eligibility for 'id' but no new format or constraint details beyond that. Baseline 3 applies when the schema carries the parameter burden.

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 concrete verb+resource pair (pin an installed app to the top of the home screen) and also covers the inverse operation via 'pinned: false', so an agent knows exactly what the call does without opening the schema. The parenthetical '(Android and iOS style)' plus the ordering rule ('after any apps pinned before it') further sharpens the semantics.

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 clear conditions: use it on installed apps, both Store apps and create_app-built apps, and toggle unpin via the pinned flag. It also names the failure condition ('Fails with not_installed'). It stops short of explicitly contrasting with hide_app or uninstall_app, so the alternative-selection guidance is implicit rather than spelled out.

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