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

Annotations already cover readOnlyHint, idempotentHint, destructiveHint and openWorldHint, so the safety profile is free. The description adds genuinely new context: the permissions model (participant, public campaign, Admin Mode admin, or owner). It omits what happens on a missing id or denied access, which keeps it short of a 5.

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?

Two tight sentences: the operation and its payload first, the access rule second. No filler, no repetition of the title or annotations.

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 needn't be explained further, and the description still summarizes the key payload (notes, battlemap refs, images). With annotations covering the read-only/idempotent profile and the one param fully documented, an agent has everything needed to call it.

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 coverage is 100% and the single param already documents itself as the Mongo `_id`. The description's 'by id' adds no format, validation, or source-of-id detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb ('Fetch') and resource ('one session by id') and enumerates what the record includes (notes, battlemap references, session-image attachments). It implicitly contrasts with the list-style siblings (play_list_campaign_sessions, play_list_my_sessions) but never names an alternative, so differentiation is inferred rather than spelled out.

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 gives an authorization condition (who may read the session) rather than a usage rule for when to pick this tool over play_list_campaign_sessions or play_list_my_sessions. Usage is implied by 'by id' but no exclusions or alternatives are stated.

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