Set Session Db

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly states that it sets a per-session override, how to clear it, how fallback works, and that it returns the new effective default. It doesn't mention any hidden side effects or persistence details beyond 'THIS MCP session', but for a simple setter this is adequate and non-contradictory.

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 three sentences with no redundancy. It front-loads the primary purpose, then explains the empty/null case and the return value. Every sentence earns its place; there is no filler or over-explanation.

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 setter with a 100% schema coverage and an output schema present, the description provides all necessary context: what it sets, when it affects, how to clear, and what it returns. Nothing an agent needs to call it correctly is missing. The presence of an output schema also means return format is documented elsewhere, so the description needn't elaborate further.

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 100%, so the baseline is 3. The description adds value beyond the schema by explicitly explaining the session-scoped effect, the consequences of passing empty/null, and the fallback to the global default. This reinforces the parameter's meaning in context and clarifies the return behavior, which the schema alone doesn't provide.

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 states a specific action (set or clear) on a specific resource (default database for THIS MCP session). It distinguishes itself from sibling query tools by focusing on session-state configuration. The phrase 'subsequent tool calls' further clarifies its role, making it unmistakable which tool this is.

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 the effect on future calls ('without an explicit db argument will use this database'), which implicitly tells the agent when to use it (to establish a session default) and when not (when explicit db arguments are always provided). It also covers clearing with empty/null and fallback to the server default, providing complete usage semantics. No explicit alternatives are named, but for a session-state tool that's not necessary.

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