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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds that it returns recent messages and that 'since' can be used for incremental fetching, which is useful behavioral context. However, it doesn't disclose pagination limits or whether messages are ordered, but with the annotation covering safety, this is adequate.

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 two short sentences, front-loading the primary function. The second sentence provides a usage tip about 'since'. It is concise and wastes no words, though it could benefit from a bit more detail on response structure.

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's moderate complexity (3 params, no output schema), the description covers the core usage and the key incremental pattern. It lacks explicit mention of 'limit' behavior or default ordering, but for a read-only message fetcher, the essential information is present. Siblings don't require deep differentiation.

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 only 33%, with only 'room' described. The description compensates by explaining 'since' as a millisecond timestamp from next_since for incremental updates, which adds meaning beyond the bare schema. However, 'limit' and the exact format of 'since' are not fully detailed, though the description helps significantly given the low coverage.

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 verb ('Read') and resource ('chat room'), and the first line 'Recent messages in a room' clarifies what the tool returns. It does not explicitly distinguish from siblings like list_rooms or search_exchange, but the focus on messages in a specific room is clear enough.

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 implies usage by mentioning 'Recent messages in a room' and the 'since' parameter for incremental fetching, but does not explicitly state when to use this vs. siblings (e.g., when to use list_rooms vs. read_room). No exclusions or alternatives are named.

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