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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds significant context by clarifying error handling in detail: 'on invalid, missing, or malformed input this tool never raises a protocol error.' This perfectly complements the annotations without contradicting them.

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 well-structured and front-loaded with the most critical information (the style, the free usage). The example is invaluable. The only minor issue is that the error handling section, while informative, could be slightly more concise without losing clarity.

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?

Despite the presence of an output schema, the description provides key return-value context by showing the exact structure of a successful response and, more importantly, the structure of all error responses. For a tool with 8 parameters (4 required), this is comprehensive and leaves no ambiguity about the tool's behavior.

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 at 100%, with all 8 parameters clearly described in the input schema. The description adds value by providing a concrete example showing how the parameters map to a citation string, highlighting that 'authors' expects 'Last, First' strings and that many parameters are optional with sensible defaults. This goes well beyond what the bare 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 clearly states the tool formats citations in APA 7, MLA 9, or Chicago style. It gives a detailed JSON example and contrasts with what the tool does not do (finding or verifying a source). This level of specificity effectively distinguishes it from siblings like 'sample_size' or 'stats_describe'.

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 explicitly states when to use the tool: 'when the source details are already known and only the formatting is missing.' It also clarifies what not to use it for: 'Not for finding or verifying a source.' While no explicit alternatives from the sibling list are named, this guidance is still quite strong.

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