As, Agni is the mouth or pedsage of the devas through which the homas are sent to them.
In verse 18 of the Isha Upanishad, Agni is invoked with, as follows mantras.:
"O Agni, you know all the paths, lead me on to success by the good path, keep me away from the wrong path of sin".
So, Agni remains close to the Sacrificer.
Agni is the Priest, Director, Brahman and Lord of the Sacrifice.:
“tava praśāstraṃ tvamadhvarīyasi brahmā cāsi ghṛhapatiśca no dame ” (RV 2.1.2).
"Thou art Director, thou the ministering Priest: thou art the Brahman, Lord and Master in our home".
Agni is the Ruler of the Sacrifice.:
“rājantamadhvarāṇāṃ ghopāṃ ṛtasya dīdivim vardhamānaṃsve dame ” (RV 1.1.8).
“[Agni] Ruler of sacrifices, guard of Law eternal, radiant One, Increasing in thine own abode".
Agni is all the gods.:
“agnirvai sarvā devatā ” (Shatapatha Brahmana 126.96.36.199)
“Agni is all the deities”
Including Vishnu, Indra, etc.:
“tvamaghna indro vṛṣabhaḥ satāmasi tvaṃ viṣṇururughāyo namasyaḥ tvaṃ brahmā rayivid brahmaṇas pate tvaṃ vidhartaḥsacase purandhyā ” (RV 2.1.3).
"Hero of Heroes, Agni! Thou art Indra, thou art Viṣṇu of the Mighty Stride, adorable: Thou, Brahmaṇaspati, the Brahman finding wealth: thou, O Sustainer, with thy wisdom tendest us".
Agni is also the highest heaven.:
वसुमतीमग्ने ते छायामुप स्थेषं विष्णो स्थानमसि । (Y V. 2.8).
Oh Agni, I have placed the earth under your shadow, and you are the supreme abode of Lord Viṣṇu.
Infact, Agni is the whole Sacrifice who gives portions to other gods by engulfing other gods in the sacrifice.:
“aghne yaṃ yajñamadhvaraṃ viśvataḥ paribhūrasi sa iddeveṣu ghachati ” (RV 1.1.4).
"Agni, the perfect sacrifice which thou encompassest about Verily goeth to all the Gods".
Thus, Agni is the lower portion, middle portion and upper portion viz the whole Sacrifice itself. And it is Agni only who distributes and enjoys the sacrifice.
And this Agni is none other then.:
“tadvā agnaya iti kriyate agnirvai sa devastasyaitāni nāmāni śarva iti yathā prācyā ācakṣate bhava iti yathā bāhīkāḥ paśūnām patī rudro 'gniriti tānyasyāśāntānyevetarāṇi nāmānyagnirityeva śāntatamaṃ tasmādagnaya iti kriyate sviṣṭakṛta iti ” (Shatapatha Brahmana 1:7:3:8).
“That (offering) then is certainly made to 'Agni,' for, indeed, Agni is THAT god;--his are these names: Sarva, as the eastern people call him; Bhava, as the Bâhîkas (call him); Pasûnâm pati ('lord of beasts,' Pasupati), Rudra, Agni. The name Agni, doubtless, is the most peaceful (sânta/aghora), and the other names of his are not peaceful (asânta/ghora): hence it is offered to (him under the name of) 'Agni,' and to (him as) the Svishtakrit”.
Agni became such like because of Lord Rudra.:
tamabravīdrudro 'sīti | tadyadasya tannāmākarodagnistadrūpamabhavadagniva rudro yadarodīttasmādrudraḥ (Sathapatha Brahmana VI-1-3-10).
'Thou art Rudra And because he gave him that name, Agni became such like (or, that form), for Rudra is Agni . (Sathapatha Brahmana VI-1-3-10).
For more, you can see this and this answers of mine respectively.
I hope this clarifies all your queries. Prd..