List databases

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

Annotations declare readOnlyHint=true, and the description reinforces that this is a read-only operation. It adds transparency about secondaries being read-only (PostgreSQL-enforced) and describes the return object structure. No contradictions with 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?

The description is concise, with three sentences covering purpose, usage context, and return format. No redundant information; every sentence adds value. Well-structured and easy to parse.

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 has no parameters and an output schema (though not shown in input, context says true), the description fully explains the tool's behavior, return structure, and how it relates to other tools. No gaps.

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 are 0 parameters (schema coverage 100%), so the baseline is elevated. The description adds meaning by explaining the role of primary and secondary databases and describes the return object (primary_id, database_ids, databases list with fields). This provides context beyond the schema.

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 'List every database this MCPg server is configured to serve', specifying the verb 'list' and resource 'databases'. It distinguishes from sibling tools by detailing the primary and secondary database concept, which is unique to this tool.

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 explains when to use this tool: to see available databases and understand which database is targeted by default. It provides context that read-capable tools accept an optional `database` argument and that writes target the primary. No explicit exclusions or alternatives are given, but the context is clear.

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