List PJSIP endpoints and registration state

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely non-obvious behavior: it falls back to chan_sip peers on older installations, which changes what the returned data means. It does not describe result ordering or volume, which is a minor 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: what it returns, when to use it, and the fallback caveat. Every sentence earns its place and the payload description is front-loaded.

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, single-optional-parameter listing tool with no output schema, the description covers the returned fields, the intended question types, and a platform-variance caveat. Nothing needed to call it correctly is missing.

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% and the single optional 'filter' parameter is already documented as a case-insensitive substring match. The description never mentions filtering, so it adds nothing beyond the schema, but the baseline of 3 applies when the schema carries the parameter semantics.

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?

Names a concrete resource (PJSIP endpoints) and the attributes returned (device state, registered contact count), so the agent knows exactly what comes back. It differentiates itself from asterisk_channels implicitly via the registration/device-state framing, but never names a sibling tool to contrast with.

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?

Provides two concrete question templates ('is extension 1001 registered', 'which phones are offline') that map cleanly onto the tool, which is strong contextual usage guidance. It stops short of saying when NOT to use it or which sibling (e.g. freeswitch_registrations, asterisk_channels) to pick instead.

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