messages_list

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral value beyond that: chronological ordering, cursor-based paging, and the default behavior when no cursor is supplied. It does not say where the cursor tokens come from, which is the one behavioral gap.

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 sentences, front-loaded with the resource and ordering, then the paging constraint, then the default. No filler. Slightly undercut by the mismatched cursor token names, which cost a point of clarity.

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?

There is no output schema, so the description must carry return-shape weight. It implies cursors exist in the response but never states what the response contains (message objects, cursor fields, has-more indicator), leaving an agent to discover that empirically.

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%, so the baseline is 3; the description earns an extra point by explaining the cursor progression model that ties before/after/page together. However, it refers to 'next_before' and 'next_after', names that do not match any schema parameter ('before'/'after'), which introduces avoidable ambiguity about what to pass.

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 and resource ('Lista mensagens') plus the ordering guarantee ('ordem cronológica'), which is genuinely useful information. It does not name or differentiate against siblings (conversations_list, conversation_get), though the resource name makes the distinction largely self-evident.

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?

Gives clear operational context: the upstream is cursor-based, not page-based, and without a cursor it returns the most recent messages. What is missing is guidance on when to reach for this versus conversation_get or conversations_list, but the when-to-use for listing messages is implied well enough.

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