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

Annotations already declare read-only, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely useful non-annotation context: the exact result fields returned, the pagination cap (20 per page, up to 4 pages = 80 results), and the billing rate ($0.003 per request).

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 short, front-loaded sentences: purpose, then return payload, then limits and cost. The field enumeration is slightly long but each sentence carries distinct information with no filler.

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 correctly compensates by enumerating the returned fields, and it also covers pagination limits and per-request cost. An agent has everything needed to call and budget the tool; only cross-tool routing guidance is absent.

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 all three parameters are already documented in the schema. The description's '20 per page, up to 4 pages' overlaps with the page parameter's schema description and adds nothing new about the query or language parameters. Baseline 3 is appropriate.

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 ('Search Substack publications by name or keyword') that cleanly separates it from post/note/user search siblings by resource type. However, it never names the closest alternatives (search_substack, search_substack_users), so the differentiation requires the agent to infer it from the noun.

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?

There is no when-to-use guidance, no alternatives mentioned, and no prerequisites. With ~90 sibling tools including several Substack search variants, the description leaves the agent to figure out on its own when this is the right tool over search_substack or search_substack_users.

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