Apollo MCP Server

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

With no annotations provided, the description carries full burden for behavioral disclosure. It states the action is 'Add contacts' which implies a mutation operation, but doesn't disclose important behavioral traits like whether this requires specific permissions, if it's idempotent, what happens with invalid contact IDs, rate limits, or error handling. The description is minimal and lacks critical operational context.

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 concise with a clear purpose statement followed by structured parameter documentation. The three-line format (purpose, args, returns) is efficient and front-loaded. However, the 'Returns: Confirmation' line is redundant since there's an output schema, making it slightly wasteful.

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 mutation tool with 2 parameters, 0% schema description coverage, and no annotations, the description is minimally adequate but incomplete. It covers the basic purpose and parameters but lacks behavioral context, usage guidelines, and error handling information. The existence of an output schema reduces the need to describe return values, but other gaps remain significant.

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 explicitly documents both parameters (list_id, contact_ids) with brief explanations, which adds value since schema description coverage is 0%. However, the explanations are minimal ('List ID', 'Contact IDs to add') and don't provide format details, constraints, or examples that would help the agent use them correctly.

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 action ('Add contacts to a list') with specific verb+resource, making the purpose immediately understandable. However, it doesn't distinguish this tool from sibling tools like 'sequence_add_contacts' or explain how it differs from other list-related operations like 'list_create' or 'lists_get'.

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 no guidance on when to use this tool versus alternatives. There's no mention of prerequisites (e.g., needing an existing list), exclusions (e.g., cannot add duplicate contacts), or comparison to similar tools like 'sequence_add_contacts' or 'contacts_search'.

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