get_list_contact_count

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

The description states 'Read-only', indicating no side effects, which is positive. However, with no annotations, it does not disclose potential error conditions (e.g., invalid list_id), rate limits, or authentication requirements. The behavioral disclosure is minimal.

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?

A single sentence that is concise and front-loaded with the key modifier 'Read-only'. Every word serves a purpose; no redundancy or wasted text.

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 simplicity of the tool (one parameter, no output schema), the description covers the core functionality and read-only nature. It could be slightly more complete by mentioning what the return value represents (the count), but overall it's sufficient.

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 schema coverage is 100% with list_id described as 'Contact list ID'. The description adds marginal value by tying it to 'one SendGrid contact list', but doesn't provide format hints or examples. Baseline 3 is appropriate as schema does the heavy lifting.

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 retrieves a contact count for one SendGrid contact list, which is specific and distinguishes it from siblings like get_total_contact_count (global count) and get_contacts_by_list (list of contacts). The 'Read-only' prefix immediately clarifies the nature.

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 when needing a count for a specific list, but lacks explicit guidance on when not to use it or alternatives like get_total_contact_count or get_contacts_by_list. The context from sibling names helps but is not directly addressed.

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