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

Annotations already declare readOnlyHint=true, so the safety profile is covered, but the description adds nothing beyond restating the title. It says nothing about behavior on a missing contact, permissions, or response shape, which is the extra context this tool should supply.

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 short, front-loaded sentence with no filler. It is efficient, though its brevity borders on under-specification rather than tightness.

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 simple two-parameter read tool with annotations and no output schema, the description is minimally viable. It omits the meaning of one required parameter and any note on missing-contact behavior, which a caller would want.

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 50%: 'id' is documented as the phonebook id, but 'contactId' has no description. The description implies a two-level lookup (contact within a phonebook) but never clarifies what contactId actually identifies, so it only partially compensates for the 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 names a specific verb and resource ('Get one contact of a phonebook'), which cleanly separates it from the list-style siblings like spokephone_list_phonebooks. It does not explicitly differentiate from spokephone_get_phonebook or the save/delete contact siblings, but the singular 'one contact' makes the scope clear.

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 instead of spokephone_list_phonebooks, spokephone_get_phonebook, or spokephone_get_directory_entry, nor any stated preconditions. The agent must infer selection 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.