check_function_availability

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. 'Check' implies a read-only operation, but the description does not explicitly state that it is safe or non-mutating, nor does it describe output format, side effects, or prerequisites. The mention of 'setup guidance' hints at behavior but lacks specifics.

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 a single sentence, efficient and front-loaded with the main verb and purpose. However, the phrase 'sampling support' is ambiguous and slightly detracts from clarity. Overall, it is concise and well-structured for the information it conveys.

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?

With no annotations, no output schema, and zero params, the description must compensate for missing context. It explains the tool's purpose and mentions setup guidance, but it does not describe what the output will look like or elaborate on 'sampling support.' Given the tool's low complexity, this is adequate but leaves gaps.

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?

The tool has zero parameters, and the schema description coverage is 100% (vacuously). With 0 params, the baseline is 4, and the description does not need to add parameter-level meaning. The description's reference to 'major Fastmail feature groups' is not a parameter but the tool's subject.

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 a specific verb+resource: 'Check which major Fastmail feature groups are available for this account and MCP client.' It distinguishes from sibling tools, which all operate on specific resources (mail, calendars, contacts), by focusing on availability and setup guidance rather than performing a specific operation.

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 implies the tool should be used when you need to know feature availability, but it does not explicitly state when to use it versus alternatives, nor does it mention exclusions. The phrase 'including setup guidance for missing...' provides some context but no concrete 'use when' or 'instead of' guidance compared to sibling tools.

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