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

Annotations already declare readOnlyHint=false, destructiveHint=true, openWorldHint=true, and idempotentHint=false, so the safety profile is covered structurally. The description adds nothing beyond that — no mention of duplicate handling, whether a returned ID is needed downstream, or rate/permission considerations — leaving behavior opaque for a destructive, non-idempotent write.

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 front-loaded sentence with zero wasted words. Brevity is appropriate, though the space freed up should have been spent on usage and behavioral context.

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 12-parameter, destructive, non-idempotent creation tool with no output schema, the description is far too thin: it does not explain return values (e.g., whether a contact ID comes back), required-field combinations, or what 'the Directory' entails. An agent could call it, but not confidently.

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 description coverage is only 17% across 12 parameters, so the description carries the burden and fails to: it only names the contact categories (already enumerated in the schema) and gives no meaning to the 10 address/name/phone fields. The single documented param (company_name) is described in the schema, not the description, so the description compensates for essentially none of the coverage gap.

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 states a specific verb ('Adds') and resource ('contact ... to the Directory') and enumerates the contact categories, which helps an agent understand the scope. It does not explicitly differentiate itself from siblings like list_contacts/get_contact, but the create-vs-read distinction is self-evident from the verb.

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?

There is no guidance on when to use this versus alternatives, no prerequisites (e.g., that company_name is required for contractors and vendors), and no warning about duplicate creation. The agent must infer the entire usage context from the name alone.

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