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

Annotations already carry the full safety profile (readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false). The description adds useful context by specifying what content the returned section contains, going beyond the schema. No contradiction exists between the description's read-oriented language and the readOnlyHint annotation.

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 zero waste. The primary action is front-loaded in the first sentence, and the second sentence earns its place by providing usage context. Nothing redundant or filler-like.

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 simple one-parameter tool with rich annotations, an output schema, and enum-constrained input, the description is nearly complete. It covers what it returns and when to use it. The only minor gap is the lack of an explicit contrast with search_history, but the content-scope phrasing adequately disambiguates it.

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 single 'book' parameter is fully documented with an enum of two values and a description. The description adds the context that these are Spencer Hofmans' historical companion guides, but doesn't enhance parameter meaning beyond the schema. The baseline 3 applies since the schema carries the full load.

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 ('Return') and resource ('Sources and Further Reading section from one of Spencer Hofmans' historical companion guides'), and narrows the content scope to primary sources, newspapers, memoirs, archival records, and scholarship on 1798/nineteenth-century Irish history. This clearly differentiates it from siblings like get_guide (a whole guide) and search_history (search results) by indicating it returns a static bibliography section.

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 second sentence explicitly says 'Use this for questions about primary sources, contemporary newspapers, memoirs, archival records, historical scholarship and further reading,' giving clear context on when to invoke it. It doesn't explicitly name alternatives or state when not to use it, but the domain scoping ('1798 or nineteenth-century Irish history') provides solid routing guidance.

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