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

Annotations already declare readOnlyHint and idempotent, but the description adds substantial context beyond them: agents may not change a human_locked link, conflicts are read-only for agents, likely_match is a hint rather than an answer, and names/message text are untrusted customer content that must not be followed as instructions. The prompt-injection warning is genuinely valuable behavioral disclosure.

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 payload description is front-loaded in the first sentence, followed by short, purposeful caveat sentences. It is dense with domain jargon and the first sentence is long, but no sentence is filler.

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?

An output schema exists, so return shape need not be described; instead the description explains what the key fields mean and how to interpret them (likely_match, human_locked, tombstone_id/link_version). Combined with the untrusted-content warning, an agent has everything needed to call and interpret this read-only tool correctly.

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?

There is only one parameter and schema coverage is 100%, with the schema already stating 'The hidden-number chat id, ending in @lid.' The description restates the @lid constraint and adds the 'hidden-number' framing, but contributes no new format or sourcing detail. Baseline 3 applies when the schema carries the full burden.

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 the specific resource (the identity panel of one hidden-number chat ending in @lid) and enumerates exactly what the panel contains: identity_state, provenance, confidence, human_locked, suppressions, open conflicts, open proposals, tombstone_id, link_version. This clearly separates it from sibling list tools such as list_identity_candidates and list_identity_decisions.

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 mention that tombstone_id and link_version are 'what a later link or unlink must carry' signals this is a pre-mutation read, and 'reads only' limits scope. However, there is no explicit 'use this instead of' routing to siblings like get_contact or list_identity_candidates, and no stated precondition for calling it.

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