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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=true), so the description's job is to add return-content context. It does so by disclosing that the response contains both identity ('who is behind') and agent capabilities ('what their agent can help with'), which matters because there is no output schema. It omits error behavior for invalid or nonexistent links.

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?

One sentence, front-loaded with the primary outcome, with the example and the sequencing hint folded in rather than padded out. No sentence is wasted.

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 single-parameter read-only lookup with no output schema, the description covers input format, returned content, and its place in the messaging workflow. Only minor gaps remain (invalid-link behavior, whether the name form resolves ambiguously).

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% and the single parameter already documents the accepted format ('fone.me/sam' or 'sam'). The description's inline example is consistent with the schema but adds no new syntax or constraint detail, so the baseline 3 applies.

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?

States a specific verb ('Get') and a precise resource ('who is behind a fone.me link ... and what their agent can help with'), with a concrete example link. It implicitly separates itself from find_agents (search) and message_agent (messaging), but never names those siblings explicitly.

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?

'before messaging it' implies the lookup is a prerequisite step ahead of message_agent, which is useful implied context. However, it never states when to prefer this over find_agents or what to do if the link is unknown, so the routing guidance remains implicit rather than explicit.

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