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

readOnlyHint=true already establishes the safety profile, so the description's added value is the disclosed matching behavior (diacritic- and word-order-insensitive) and the return shape: per-app identities grouped when names match, plus shared conversations with DMs first. That is meaningful behavioral context beyond the annotation, though it says nothing about ambiguity, truncation, or empty results.

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?

Two sentences, zero filler, and the distinguishing detail (diacritics/word-order tolerance) is placed immediately after the purpose so the agent gets the key behavior first, followed by return-shape expectations.

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?

One required parameter, 100% schema coverage, a readOnly annotation, and no output schema — the description compensates by describing what comes back (grouped identities, conversations, DM ordering). Little an agent needs in order to call it correctly is missing.

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 documents the single query parameter, yet the description still adds real semantics the schema lacks: matching is fuzzy on diacritics and word order and covers nickname/email variants, which is exactly what an agent needs to choose a query string.

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?

Names a specific verb and resource (find a person) plus the matching fields (name, nickname, email) and scope ('across all accounts'), which cleanly separates it from siblings like search_messages, list_accounts and list_conversations.

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?

Usage is implied rather than stated: the 'across all accounts' scope and the matching examples suggest this is the entry point for people lookup, but the description never says when to prefer it over search_messages or list_accounts, nor any exclusion such as ambiguous or multi-match cases.

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