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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so the safety profile is covered without the prose; the description's "changes nothing" is reinforcement, not new information. Genuinely additive detail is thin: get returns filters plus a contact count, and list is paginated. The bulk of the behavioral disclosure (contact_filters replaces the whole list, contacts are kept on delete) describes mutations this tool refuses, so it does not help an agent invoke this tool correctly.

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 first paragraph is tight, front-loaded, and earns every sentence. The second paragraph is roughly twice as long and spends most of its words on actions the schema enum excludes, which is wasted space for a two-action read tool. Structure is fine, but the payload is bloated with inapplicable content.

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 read-only tool with a nested contact_filters object and no output schema, the description should focus on what list and get return and how filtering/pagination behaves. Instead it documents the mutation surface, leaving the agent with no added detail on list response shape beyond "paginated, with filters." The `get_contact_filter_types` pointer is helpful but is framed around building filters, which only matters for the actions this tool refuses.

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 100%, so the schema already documents id, page, and per_page including defaults and the max of 100. The description restates those same parameters without adding syntax or format meaning. The remaining parameter discussion covers create/update fields that the action enum does not permit here.

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 opening sentence is precise: "Read segments — this tool changes nothing. Actions: list, get," and it names the sibling that owns writes (`segments_manage`). It also defines what a segment is (saved sets of contact filters that campaigns target), which no schema field conveys. However, the second paragraph then enumerates create/update/delete actions the tool does not expose, muddying an otherwise crisp scope statement.

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?

Explicit routing is present: writes are refused here and belong to `segments_manage`, and the agent is told to call `get_contact_filter_types` first when building filters. The exclusion is stated up front rather than left to inference. The guidance loses a point because the subsequent create/update/delete parameter coaching applies to an action set this tool rejects, so the agent must self-filter which advice is actionable.

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