List activity

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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuinely new context: 'Reading the list marks nothing read', grouped items aggregated with a people count, and pagination via next_cursor. It stops short of describing rate limits or empty-state behavior, but the safety profile is well complemented.

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 what the list contains, then behavior, then paging — no filler sentences. Slightly dense with response-field detail (comment_id, on_post_id) that could be tighter.

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 usefully describes the returned shape (type, from, people, comment_id, on_comment_id, on_post_id) and the paging contract. Complete enough for a zero-required-parameter list tool; only edge behaviors like empty results are unstated.

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%, so both cursor and the filter enum are already documented in the schema; baseline 3 applies. The description adds no parameter syntax or format detail beyond repeating that paging uses next_cursor and enumerating the 'type' names, which are response fields rather than inputs.

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 resource (Substack notifications / Activity tab) with the concrete item types it contains (replies, likes, new followers, restacks) and the ordering (newest first). An agent can tell this apart from list_comments, list_note_replies and get_unread_counts 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?

The description implies the use case (reading the Activity tab, paging with next_cursor) and explains the filter values, but never names an alternative or says when to prefer this over list_comments, list_note_replies, or get_unread_counts. Usage is inferable rather than stated.

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