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

With annotations present, the bar is lower, and the description still adds genuinely useful behavior: the call is non-mutating, it returns a preview plus a confirmation link, and only the merchant on that page can complete the install. This human-in-the-loop detail is exactly the kind of context annotations cannot convey. Mild tension with readOnlyHint=false (the description says the call 'changes nothing'), which is not resolved, keeping it from a 5.

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 mutating-behavior caveat is front-loaded and well placed, but the 'Money is integer minor units (cents)' sentence is dead weight — there is no monetary parameter in this tool — and it dilutes an otherwise tight description.

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 no output schema, the description correctly carries the return-value burden by describing the preview and confirmation link, which is what an agent needs to interpret the result. The stray money sentence is a minor blemish on an otherwise complete picture for a one-parameter tool.

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?

There is a single parameter with 100% schema description coverage, so the schema already carries the semantics. The description's only parameter-adjacent sentence ('Money is integer minor units (cents)') refers to a money parameter that does not exist in the schema, adding no value and risking confusion.

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+resource combo (install or update a free plugin), which cleanly separates it from read-only siblings like plugins_available and plugins_list. It does not, however, explicitly distinguish itself from plugins_set_enabled or plugins_settings, which an agent could plausibly confuse with 'installing/enabling'.

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?

It establishes clear usage context: this is for *free* plugins, and the call is a non-binding preview that requires the merchant to confirm on a separate page. The schema's 'as plugins.available gives them' hints at the discovery prerequisite, but no sibling tool is named as an explicit alternative the way a 5 would require.

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