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

Annotations already declare readOnly/idempotent/non-destructive, so the description adds context beyond them: results are bucketed into people/posts/Notes and later pages may contain only posts and Notes. That pagination-shape caveat is genuinely useful behavioral detail.

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?

Three sentences, front-loaded with the action and result shape, then follow-on tool IDs, then the paging caveat. Every sentence carries information.

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 responsibly describes the return grouping and pagination behavior. It could note result ordering or empty-result behavior, but an agent has enough to invoke and consume it correctly.

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 both query and cursor are already documented, and the description only reinforces that cursor comes from next_cursor. No additional semantics 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+resource ('Search all of Substack') and enumerates the result types (people, posts, Notes), which clearly separates it from sibling listers like get_feed, list_posts, or list_notes.

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?

Explains when the result is useful by naming the downstream tools (follow_user, like_post, reply_to_note, send_message, recommend_publication) and clarifies paging via next_cursor. It lacks an explicit contrast with alternatives like get_feed, so not a full 5.

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