Get current WAL LSN

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

Annotations indicate readOnlyHint=true, and the description reinforces no side effects. Importantly, the description adds behavioral details beyond annotations: it explains primary vs standby behavior, version support, and the exact return format. No contradictions.

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 description is two sentences plus an example, front-loaded with core functionality. Every sentence adds value: primary/standby behavior, workflow context, version support, return structure. Concise and well-organized.

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?

Given the tool's simplicity (one optional parameter, clear return object), the description is complete. It explains primary/standby behavior, version compatibility, and the role/lsn return structure. With annotations and output schema present, no further details are needed.

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 input schema has 100% description coverage for the single optional parameter 'database', specifying it targets a secondary read-only database. The description does not add additional meaning beyond the schema, meeting the baseline of 3.

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 tool name and title clearly indicate it returns the current WAL LSN. The description specifies it returns pg_current_wal_lsn on a primary and pg_last_wal_replay_lsn on a standby, distinguishes it from sibling tools like wait_for_lsn, and explains the return structure (role and lsn). This is specific and action-oriented.

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 provides a usage workflow: capture LSN on primary after write, pass to wait_for_lsn on standby before read. This gives clear context for when to use the tool. It does not explicitly state when not to use it or list alternatives, but the workflow guidance is strong.

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