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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, so the description does not need to restate safety. It adds useful behavioral context: Pipeworx fronts an API key by default, callers may pass their own as _apiKey, and results include title, creator, date, subjects, rights, holding institution and object link. It does not disclose pagination limits or rate-limit behavior beyond the schema.

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?

The description is front-loaded with the core search scope and is organized around sources, filters, return fields, alternatives, auth and an example. It is somewhat long, especially the institutional source list, but the detail is relevant and not repetitive.

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 12-parameter, read-only search tool with no output schema, the description covers scope, available filters, return fields, authentication behavior, alternatives and an example. Combined with the annotations and fully documented schema, an agent has enough context to invoke 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 description coverage is 100%, so the schema already defines all 12 parameters and baseline is 3. The description adds value by grouping the filters in plain language, giving an example invocation, and clarifying the default-key versus user-supplied _apiKey behavior.

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 states a specific verb and resource: search roughly 50 million digitised items aggregated by the Digital Public Library of America. It lists content types and source institutions, and explicitly positions the tool against generic web search, so an agent can tell what it is for 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?

It gives clear usage context, especially 'PREFER OVER WEB SEARCH for American primary sources', and explains the API-key situation. It does not explicitly differentiate from sibling tools like dpla_item or dpla_collections, though it cross-references dpla_collections for the collection parameter.

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