brain_session_resume

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

This is an annotation contradiction. The description frames the operation as a lifecycle mutation ('resume', 'lifecycle boundary'), and the input schema mentions guarding 'any session mutation', while annotations declare readOnlyHint=true. An agent cannot trust whether this tool changes session state.

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 short sentences, with the primary action and trigger front-loaded and the important system-level restriction stated immediately after. There is no filler; every sentence earns its place.

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?

The trigger restriction is clear, but the tool is incomplete for a lifecycle operation: the reader is not told what resuming actually changes, whether the session must already be open, or how expected_client_key mismatch is handled. The annotation contradiction further undermines the safety profile, so the presence of an output schema does not make this definition sufficient.

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?

The description adds minimal semantic value by indicating session_id should refer to an open session, while expected_client_key is already well described in the schema. It does not explain what happens on a client-key mismatch or where the expected client key comes from, but the parameter-level meaning is at least minimally viable.

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 clearly states the action (resume), object (an open session), and trigger (an explicit user command). It distinguishes this from lifecycle siblings by emphasizing the user-command boundary, but it does not explicitly name an alternative tool or detail what resuming entails, so it falls just short of full sibling differentiation.

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 description explicitly says this is for an explicit user command and that hooks and auto-close must not invoke this lifecycle boundary, giving clear when and when-not guidance. It does not mention how to handle a non-open session or when to prefer a sibling tool such as brain_session_start, so it is not fully complete.

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