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

readOnlyHint=true already tells the agent this is a safe read. The description adds meaningful value beyond that, disclosing the payload contents (name, contact counts by status, created_at) and identifying the underlying endpoint GET /lists/{list_id}. It does not mention auth or rate limits, but for a simple read that is minor.

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 tight sentences with the core action front-loaded. The trailing API endpoint reference is slightly redundant for an agent but compact and harmless.

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 burden of describing returns falls on the description, and it does list the main fields an agent would receive. Combined with the readOnly annotation and a fully documented single parameter, this is nearly complete; only the exact shape of the contact-count breakdown is left implicit.

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?

Only one parameter, fully documented in the schema with 100% coverage. The description's 'by its id' adds no syntax or format detail beyond the schema, so the 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?

States a specific verb (get) and resource (a single list by id), which implicitly separates it from list_lists's collection view. It never names the sibling tool outright, so the differentiation rests on the reader noticing 'single' vs. list 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?

Usage is only implied: fetch one list when you already have its id. There is no explicit when-to-use statement, no condition for preferring this over emailoctopus_list_lists, and no prerequisites mentioned.

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