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

Annotations already declare readOnlyHint=true and destructiveHint=false, yet the description adds material behavioral caveats: the LIMITATION that install date/installer is not stored, that `description` is only populated for custom extensions (so agents must not guess built-in behavior), and the ID-handling rule. It stops short of describing result shape or ordering, but clearly exceeds what the annotations convey.

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?

Front-loaded with the core distinction before the caveats, and every sentence carries routing or field semantics. It is slightly dense and telegraphic (multiple em-dash asides, ALL-CAPS emphasis), which costs a little readability, but there is no filler.

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 parameters, no output schema steps, and rich annotations, this description supplies everything else an agent needs: scope, sibling disambiguation, field semantics for the returned rows, an explicit data limitation, and a pointer for the follow-up question. Complete for the tool's complexity.

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?

The tool takes zero parameters, so the baseline is 4. The description still adds field-level meaning for the response (extensionId vs companyExtensionId), which is a bonus rather than a requirement given there is nothing to parameterize.

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 (list installed extensions) and immediately distinguishes scope: built-in and organisation-built extensions this company actually has. It explicitly names the sibling it is not (get_extension_catalog) and frames the user questions it answers, so an agent can route without opening either schema.

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 ('which extensions do I have', 'is WooCommerce turned on for me'), an explicit when-not with the alternative (get_extension_catalog lists the whole platform regardless of install), and a second routing pointer (get_extension_surfaces for cabinet changes). Nothing is left to inference.

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