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

The description is consistent with readOnlyHint=true and openWorldHint=false, and it adds a genuinely useful caveat that "Identity proves key possession, not trust." However, it does not explain the auth flow (that a session_token from a prior prove is required) or what the returned identity card looks like, leaving the agent to infer behavior from the schema and annotations.

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 compact sentences with the resource stated up front and the trust caveat at the end. The parenthetical list of facts is efficient, though "worth keeping in your memory" is slightly informal 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?

For a simple single-parameter read with no output schema, the description supplies the key value: it names the fields the agent will receive and its trust limitation. The only gap is the prerequisite relationship to the session token flow, which the schema partially covers.

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 a single session_token parameter with 100% schema description coverage, including its 43-character constraint and Bearer transport. The description adds nothing about how the token relates to this call, so 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 and resource: "Read your own identity and your identity card," and enumerates the facts returned (gateway, agent_id, key location). This is clearly distinct from agent_authenticate's apparent purpose, though the definition never explicitly names that sibling to sharpen the contrast.

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?

The phrase "worth keeping in your memory" implies the intended usage pattern—fetch once and retain the facts—but there is no explicit when-to-use, when-not-to-use, or named alternative such as agent_authenticate.

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