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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds valuable context beyond that: results are public replies returned in the same shape as substack_note, and the operation is cursor-paginated. It doesn't state rate limits or ordering, but it goes beyond the annotations.

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 short sentences, zero waste, front-loaded with the resource and immediately followed by the pagination contract. Every clause earns its place.

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?

An output schema exists, so return-value detail is unnecessary; the description usefully notes the element shape and pagination. For a two-parameter read-only list tool this is essentially complete, with only minor gaps (ordering, reply counts) that don't impede correct invocation.

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 description coverage is 100%, with both cursor and note_id documented in the schema. The description restates the cursor contract but adds no syntax or format detail beyond the schema, so the baseline of 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 (List) and resource (public replies to a Substack Note), and implicitly distinguishes itself from the sibling substack_note (the Note itself) and substack_note_restacks (restacks, not replies). An agent can tell what this returns without opening the 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 clear procedural context for pagination: pass the previous response's next_cursor back as cursor. It does not explicitly state when to prefer this over sibling tools like substack_note or substack_note_restacks, but the purpose statement makes the selection obvious.

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