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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, covering the safety profile. The description adds valuable behavior context by specifying what metadata is returned and that the tool is a preliminary step for retrieving text. This goes beyond the annotations, explaining the tool's role and output structure without contradicting any hints.

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 two sentences with no wasted words. The first sentence front-loads the main purpose and enumerates the returned fields concisely. The second sentence adds essential usage guidance. Every sentence earns its place, and the structure is clean and scannable.

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?

The tool has an output schema (as noted), so detailed return-value documentation is not required in the description. The description lists the key metadata fields and provides a clear use case. It is complete for a single-parameter read-only tool, though it doesn't explicitly mention the output schema's structure. Overall, nothing critical is missing for correct invocation.

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%, and the schema's description for the 'id' parameter is very detailed, including examples and how to obtain the ID. The tool description adds only minimal reinforcement ('by ID') and does not provide additional parameter semantics beyond the schema. Since the schema is comprehensive, the baseline of 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?

The description states a specific verb ('Fetch'), a specific resource ('complete metadata for a Project Gutenberg book by ID'), and enumerates the exact fields returned (title, authors, translators, editors, subjects, etc.). It clearly distinguishes itself from the sibling tools by focusing on a single book's metadata, and explicitly references gutenberg_get_text as a follow-up. This differentiates it without ambiguity.

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 provides explicit usage guidance: 'Use this before gutenberg_get_text to confirm a plain-text format is available and to get the direct download URL.' This tells the agent when to invoke this tool and why, while implying that gutenberg_get_text is for the actual text content. It gives a clear workflow context.

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