List Note replies

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

Beyond the readOnly/idempotent annotations, it discloses ordering (Substack's order) and two non-obvious data quirks: author.handle is empty and url is null because Substack sends no handle with replies. It also states pagination happens via next_cursor. These are exactly the surprises that would otherwise mislead an agent parsing results.

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?

Four short sentences, front-loaded with what the tool returns, then scope, then quirks, then pagination. No filler. The opening sentence being a bare noun phrase rather than a full clause is a minor structural weakness.

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 carries the burden and does so well: it names the returned fields, ordering, null-handling, and pagination. It stops short of saying whether pagination terminates or how deep reply nesting goes, which an agent calling repeatedly would want.

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 the baseline is 3, but the description adds real meaning: note_id points at 'one Note' whose replies you want, and it explicitly warns that the `replies` field is a count that can itself be passed as a note_id. That disambiguates a confusing name collision the schema alone would not.

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 second sentence states precisely what is returned: 'the direct replies under one Note (yours or anyone's), in Substack's order.' That distinguishes it from list_notes (top-level notes) and reply_to_note (a write). The first line is a fragment ('Replies under a Note, with author, text and likes') but the following sentence supplies the verb and scope.

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 clarifies the scope is one Note, 'yours or anyone's', and gives an actionable recursion rule: reply objects carry a `replies` count, and you drill in by passing that as note_id. It does not explicitly name alternatives such as list_notes or get_conversation, so it falls short of full when/when-not routing.

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