pyfastmail-mcp

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

No annotations are provided, so the description carries full burden. It states it 'Get full details' but doesn't disclose behavioral traits such as whether this is a read-only operation, potential error conditions (e.g., invalid href), authentication needs, rate limits, or what 'full details' includes. The description is minimal and lacks necessary context for safe invocation.

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 appropriately sized with two sentences: one stating the purpose and another detailing the parameter. It's front-loaded with the core function. However, the second sentence could be more integrated, and there's slight redundancy in specifying 'href' twice.

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?

Given the tool has an output schema (which handles return values), no annotations, and a simple parameter structure, the description is moderately complete. It covers the purpose and parameter semantics adequately but lacks behavioral transparency (e.g., safety, errors) and more explicit usage guidelines, leaving gaps for an AI agent to infer 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?

The description adds meaningful semantics beyond the input schema, which has 0% coverage. It explains that 'href' is 'The href/URL path of the vCard resource' and specifies it should be 'as returned by contacts_list', clarifying the parameter's purpose and source. With only one parameter, this is sufficient to compensate for the schema's lack of description.

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 verb 'Get' and resource 'full details of a single contact', specifying it's by 'CardDAV href'. It distinguishes from sibling tools like contacts_list (which lists) and contacts_create_contact (which creates). However, it doesn't explicitly contrast with contacts_update_contact or contacts_delete_contact beyond the verb difference.

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 usage by stating the href should be 'as returned by contacts_list', providing some context for when to use this tool. However, it lacks explicit guidance on when to choose this over alternatives like contacts_list (for bulk retrieval) or other contact tools, and doesn't mention prerequisites or exclusions.

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