read_messages

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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds the ordering guarantee, the pagination mechanic, and a prompt-injection warning about untrusted message text, which is meaningful extra behavior. It still omits backfill limits (does it reach full history?) and rate/volume behavior.

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?

Three short lines, zero filler: scope and ordering first, then the paging rule, then the security caveat. Every sentence earns its place.

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 no explanation, and the description covers scope, ordering, paging, and the injection risk. Minor gaps remain around accepted chat identifier formats and whether pagination eventually exhausts history.

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%, so the description carries the burden. It explains the non-obvious parameter well (offset_id = smallest id seen, i.e. a cursor rather than a page index) but leaves chat, limit, and from_me_only undocumented, relying on self-evident names.

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?

Description states a specific verb and resource ('Read recent messages in a chat') plus an ordering guarantee ('newest first'), which distinguishes it from the sibling search_messages. It never names the sibling or clarifies the boundary explicitly, so it stops short of a 5.

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?

It gives concrete paging guidance ('Page back with offset_id = smallest id seen'), which is real operational advice. However, it says nothing about when to prefer this over search_messages, list_chats, or mark_as_read, and gives no exclusions or preconditions.

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