Find a free textbook

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

Goes well beyond the readOnly/openWorld annotations: discloses that no account or key is required, that Open Library results are tagged 'free' vs 'borrow', and that partial source outages still return results with the failed source named. That failure-mode and result-tagging behavior is exactly the kind of context annotations cannot convey.

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-loads the core action and sources before listing inputs and behaviors, and every clause carries information. It runs slightly long, with the trailing example prompt being helpful but not essential.

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?

An output schema exists, so return-value detail is appropriately omitted. The description still covers sources, parameter interpretation, result labeling, and degraded-mode behavior, leaving nothing an agent needs in order to call 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 the schema already documents both params. The description still adds meaning: query accepts a title, ISBN, or course topic, and the limit applies 'from each source' rather than as a total cap — a distinction the schema does not make.

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 for free and legal copies of a textbook') and names the three concrete sources it queries. It is clearly distinguishable from siblings like lookup_isbn (metadata) and find_older_edition (edition history) because it is the only one framed as a multi-source free-copy search.

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?

Gives a clear triggering context and even a sample user prompt ('Is there a free legal copy of the Calculus textbook by Stewart...'), which makes the intended use concrete. It does not explicitly say when to prefer lookup_isbn or find_older_edition instead, so routing between siblings is left partly to inference.

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