session_statistics

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It implies a read operation by saying 'Get detailed statistics', but it never explicitly states that the tool is side-effect-free, what happens when the agent_id does not belong to the session, or whether there are rate limits or data-freshness concerns. The only behavioral constraint is the parenthetical 'must belong to the session'.

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 well-structured with trigger bullets, an output summary, and parameter notes, but it has some redundancy: the fragment 'Messages, agents, artifacts, and timing' is essentially repeated by 'Includes message counts, breakdown by type and agent, artifact count, and time range.' Still, the overall length is reasonable and the key information is easy to scan.

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 two-parameter read-style statistics tool with no output schema, the description covers the essential inputs, the membership constraint, and the main return categories. It does not describe exact output structure or failure behavior, but those are not critical enough to make the description incomplete for basic invocation.

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%, and the schema only provides property titles 'Session Id' and 'Agent Id'. The description compensates by explaining that session_id is the session to get statistics for and agent_id is the caller's ID that must belong to the session, adding meaning and a constraint beyond the bare 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 the tool gets detailed statistics for a session and enumerates the included dimensions: messages, agents, artifacts, and timing. It is specific enough to understand what the tool does, though it does not explicitly differentiate itself from overlapping siblings like sessions_summary or session_recap.

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 AUTOMATIC TRIGGERS section gives concrete example queries and use cases, such as 'How active was this session?' and comparing sessions by message volume. It provides clear when-to-use guidance, but it does not mention when not to use this tool or identify alternatives.

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