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

Annotations already cover the safety profile (readOnly, non-destructive, open-world), so the bar is low, and the description adds real context: an auth requirement (Cotlet API key with app access), ordering (newest first), pagination size (50 per page) and how to advance (next_cursor as cursor). It stops short of describing rate limits or response shape, keeping it at 4.

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 and generally efficient, with the List scope stated first. But the first and second sentences overlap heavily ('posts of your publication, newest first' is repeated nearly verbatim), which is a redundant clause that does not fully earn 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?

For a read-only list tool with full schema coverage and annotations carrying the safety profile, the description covers ordering, filtering, pagination, and auth requirements. With no output schema, slight gaps remain (no explicit note on total counts or empty results), but nothing essential to correct invocation is missing.

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; the description nonetheless adds meaning beyond the schema by explaining the status filter (drafts vs scheduled), that scheduled posts carry a publish time, and the cursor-chaining pattern ('pass next_cursor back as cursor'). That extra pagination semantics earns above baseline.

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 and resource ('Lists posts of your publication') and pins down scope with 'newest first, with status and audience.' An agent can distinguish it from siblings like substack_get_post (single post) or substack_create_draft without opening a 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?

It tells the agent to 'filter by status to see drafts or scheduled posts,' which is useful implied usage context. However, it names no alternatives or exclusions (e.g., when to reach for substack_get_post or substack_get_post_stats instead), so routing guidance is only partial.

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