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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is partly covered. The description adds that the key must be previously issued and that activation is session-scoped, but it does not disclose what happens with an invalid or expired key, whether the session activation persists, or how it interacts with other auth flows.

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 sentence with the purpose front-loaded and the qualifying condition appended. No filler, no restatement of the title.

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 one-parameter, no-output-schema session-auth tool, the description covers what it does, what it needs, and when to reach for it. The remaining gap is the relationship to sibling auth tools (ucode_authenticate, ucode_connect, ucode_login_start) and failure behavior, which is minor at this complexity.

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 0%, so the description must carry some of the burden; it does clarify that the single apiKey parameter is a previously issued uc_live_ key, which matches the schema's pattern. That is modest added value over the raw pattern constraint, but it gives no guidance on sourcing or handling the key.

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 gives a specific verb (Activate), a specific resource (a previously issued uc_live_ agent API key), and the scope of the effect (this MCP session). It implicitly separates itself from the header-based auth path used by sibling tools like ucode_authenticate, though it does not name any sibling tool 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?

The parenthetical "for clients that cannot set an Authorization header" states the precise condition under which this tool is the right choice, which is genuinely useful routing information among many auth-related siblings. It stops short of naming an alternative tool or stating an explicit when-not-to-use case.

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