session_undo

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

With no annotations, the description carries the full burden. It usefully discloses scope ('last successful mutating operation') and mechanism ('session snapshot journal'), implying a one-step, journal-backed reversal. It omits failure behavior (what happens with no snapshot), whether the undo is itself reversible, and any auth or session-precondition requirements.

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 front-loaded sentence with no filler; the operative action and its scope appear immediately.

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?

An output schema exists, so return values need not be explained, and the mutation's intent is clear. However, for a state-changing tool with no annotations and an undocumented session_id, the description should say more about preconditions and failure cases to be fully actionable.

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% for the single required parameter session_id, and the description never mentions it or explains what value it takes (e.g., from session_create/session_list). Since the schema does not document the parameter, the description should have compensated and does not.

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 and resource ('Undo the last successful mutating MCP operation') plus the mechanism ('session snapshot journal'), which is far more precise than the bare name. It does not, however, explicitly distinguish itself from the sibling session_redo, leaving the agent to infer the undo/redo pair from naming alone.

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?

There is no guidance on when to use this versus session_redo, no mention of prerequisites (an existing session, a populated snapshot journal), and no stated limit such as whether only a single operation can be undone. Usage is only implied by the name and the word 'last'.

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