Search Substack publications

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds behavioral context beyond annotations by revealing that results include canonical host information and that this is specifically required by research tools, which is useful for agents deciding whether the output is adequate.

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?

Two sentences with no filler. The first sentence states the action and scope; the second explains the output's significance. Every word earns its place, and key information is front-loaded.

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 straightforward read-only search tool with fully documented parameters and safety annotations, the description adequately covers what the tool does and what it returns. The lack of an output schema is partially mitigated by stating that each result includes a canonical host. It could have mentioned result count or sorting, but those are minor gaps given the tool's simplicity.

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 the schema already documents all four parameters. The description's mention of 'name or topic' loosely reinforces the query parameter's meaning but adds no new detail about pagination, limits, or the publication parameter beyond what the schema provides.

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 description uses a specific verb and resource: 'Search Substack for publications by name or topic.' It also explains the key output (canonical host) and why it matters, which clearly distinguishes this publication-search tool from sibling tools like search_posts that target posts rather than publications.

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 gives a clear context for when to use this tool: it returns the canonical host that research tools need for custom-domain publications. This implies using this tool before research tools when a publication is on a custom domain, but it does not explicitly mention alternatives or exclusions such as 'use search_posts for post-level searches.'

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