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

Annotations set idempotentHint=false, which contradicts the description's 'fetch' semantics (read-only operations should be idempotent). The description does not explain why the tool is not idempotent or mention any side effects. This inconsistency harms transparency.

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 followed by a large JSON blob listing filterable fields. While informative, the JSON is verbose and could be summarized (e.g., 'Supports filtering by any property from the output schema'). The structure is adequate but not elegantly concise.

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 presence of an output schema (inferred from parameter descriptions) and readOnlyHint=true, the description omits behavioral details like pagination behavior, default sorting, or result format. It is functional but lacks nuance about what is returned or how to handle large result sets.

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 coverage is 100% with all parameters described, but the description adds significant value by listing the exact filterable properties (e.g., id, caller, duration) in a JSON object. This goes beyond the schema's generic filter structure, helping agents construct precise filters.

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?

Description clearly states 'Fetch voicemail messages from VoIPstudio', specifying the action (fetch) and resource (voicemails). It also lists supported filter fields, making the tool's scope unambiguous. Sibling tools (e.g., get_recordings, get_cdrs) are distinct, so no confusion.

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 for fetching voicemail messages but provides no explicit guidance on when to use vs. alternatives (e.g., when to use get_recordings instead). No when-not or prerequisites are mentioned, leaving the agent to infer context from sibling names.

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